Comparative Analysis on Household Energy Consumption Behavior in Asia Megacities by Considering the Effects of Car Ownership and Self-selection

Transcription

1 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 Comparatve Analyss on Household Energy Consumpton Behavor n Asa Megactes by Consderng the Effects of Car Ownershp and Self-selecton Byng YU Doctor Canddate Graduate School for Internatonal Development and Cooperaton, Hroshma Unversty, -5- Hgash Hroshma, Japan Fax: E-mal: yubyngjapan@yahoo.co.jp Juny ZHANG Assocate Professor Graduate School for Internatonal Development and Cooperaton, Hroshma Unversty, -5- Hgash Hroshma, Japan Fax: E-mal: zjy@hroshma-u.ac.jp Amasa FUJIWARA Professor Graduate School for Internatonal Development and Cooperaton, Hroshma Unversty, -5- Hgash Hroshma, Japan Fax: E-mal: afujw@hroshma-u.ac.jp Abstract: In order to understand the energy consumpton patterns of dfferent ctes wth vared economc development level n Asa, as well as examne the effects of car ownershp and self-selecton on household energy consumpton behavor, four representatve megactes, Toyo, Bejng, Jaarta, and Dhaa were selected and a uestonnare survey about household energy consumpton coverng more than, households was conducted at each cty n 29. Based on the survey data, Hecman s latent ndex model s further bult for each cty by separatng the effect of the car ownershp tself and the effect of self-selecton. The results showed that, on average, the effect of car ownershp tself on the ncrease of household energy consumpton accounts for 9.3% n Toyo, 86.59% n Bejng, 78.3% n Jaarta, and 69.7% n Dhaa. Whle the effect of self-selecton accounts for 9.87% n Toyo, 3.4% n Bejng, 2.69% n Jaarta, and 3.93% n Dhaa. Key words: comparatve analyss, household energy consumpton behavor, car ownershp, self-selecton. INTRODUCTION In recent years, Asan regon s consumng ncreasng amounts of energy. Snce 99, consumpton has rsen by two thrds, largely drven by mddle-ncome economes such as Chna and Inda, where energy has been used to fuel rapd economc growth. Furthermore, to 23 the ncrease of energy consumpton n Asa s estmated to account for 46% n the total world energy ncrease (ESCAP, 29). Household energy consumpton s expected to ncrease throughout the Asan regon together wth rsng per capta ncome, lvng standards, and lfestyles, and conseuently t s mportant to 724

2 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 analyze household energy consumpton behavor n order to formulate polces for promoton of sustanable energy consumpton (ESCAP, 29). Household energy consumpton ncludes n-home energy consumpton caused by the usage of coolng, heatng, electrc applances (e.g., electrcty, gas, erosene) and out-of-home energy consumpton caused by the prvate vehcle usage, le gasolne. Statstcs shows that n-home energy consumpton n Asan countres has sgnfcantly ncreased wth the growng penetraton rate of dfferent applances durng the last decade (the annual growth of household electrcty s 3.8 percent whch s much hgher than 2. percent of OECD countres). Regardng to the out-of-home energy consumpton, strong economc growth coupled wth low car ownershp rates and rsng ncomes has turned Asa nto a gold mne for the automotve ndustry. The annual growth rate of Asan transport energy demand to 22 s projected to be 4.33 percent (the world level s 2.4 percent) (Urban Transport Energy Effcency 26). Moreover, n some Asan countres (e.g., Japan, Korea, Indonesa), out-of-home energy consumpton caused by prvate vehcle travel accounts for nearly 5% of the total household energy consumpton, whch suggests that the car ownershp choce has a sgnfcant nfluence on the household energy consumpton behavor (World Energy Outloo 26). Accordngly, accumulaton of nowledge on the energy consumpton patterns, as well as the relatonshp between car ownershp and household energy consumpton n Asan ctes s very essental to assst n formulatng adeuate measures to cope wth the envronmental problems foreseen n the future. In general, households select whether to own a car or not based on ther socal-demographc attrbutes, travel needs, atttudnal factors (e.g., envronmental awareness, specal taste on drvng) and so on. The objectve factors le socal-demographc attrbutes can be easly captured through the survey; however the subjectve psychologcal factors le envronmental awareness are dffcult to derve exactly. In order to deeply understand the relatonshp between car ownershp and household energy consumpton behavor n Asan ctes, self-selecton s proposed to dsentangle the effect of car ownershp on household energy consumpton. In statstcs, self-selecton arses n any stuaton n whch ndvduals select themselves nto a group, causng a based sample wth nonprobablty samplng. It s commonly used to descrbe stuatons where the unue characterstcs of the people whch mae them to select themselves nto the group whch creates abnormal or undesrable condtons n the group. In the context of fully consderng objectve factors, the self-selecton s expected to be the unue subjectve characterstcs of households n ths study, such as some motvatonal factors, envronmental awareness, specal taste on drvng and so on. Regardng to the effect of self-selecton on household energy consumpton behavor, t covers two parts: the drect effect on vehcle travel and the ndrect effect on n-home energy consumpton behavor. For nstance n realty, some people may choose to use publc transportaton nstead of buyng a car due to ther hgh envronmental concern whch would also nfluence the n-home energy consumpton behavor, such as the ownershp (choosng to buy energy effcent types) and usage (leadng an energy-savng lfestyle) of n-home applances. Whle certan ndvduals mght have a specal taste on drvng, n ths case the household wll choose to buy a car regardless of other lmtatons, and put a heaver use on t whch ncreases the gasolne consumpton but meanwhle alters the tme allocaton for dfferent actvtes whch may change the n-home energy consumpton pattern. Conseuently, the observed dfference n household energy consumpton between car ownng households and no car households s a comprehensve product of car ownershp, self-selecton on out-of-home energy consumpton behavor, and self-selecton on n-home energy consumpton behavor. As a result, the predcted ncrease of household energy consumpton caused by the 725

3 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 change of car ownershp would be based f households self-selecton help determne the car ownershp. Under such crcumstances, amng at explorng dverstes between car ownershp and energy consumpton behavor, ths study selects four representatve megactes wth vared economc development level n Asa, ncludng Toyo, Bejng, Jaarta, and Dhaa, the captal of Japan, Chna, Indonesa, and Bangladesh, respectvely. A household energy consumpton survey was conducted n each cty n 29 to collect the nformaton about the n-home/out-of-home expendtures and energy consumpton behavors referrng to ownershp and usage of end-uses, as well as the soco-demographc attrbutes of households and ther representatve members. Based on the comprehensve survey data, aggregaton analyss and Hecman s latent ndex model (Hecman, 976, 979) are conducted to explore the dverse cause-effect relatonshps n these four megactes among car ownershp, household attrbutes, end-use ownershp, and energy consumpton. Besdes, the relatve effects of car ownershp and self-selecton on household energy consumpton are separated and uantfed by usng the latent ndex model. The remanng part of ths paper s organzed as follows. The next secton brefly revews exstng surveys and lterature on household energy analyss. Secton 3 llustrates the models used n ths study. The survey data and relevant aggregaton analyses are explaned n Secton 4. Estmaton results of models are shown n Secton 5. Ths study s concluded n Secton REVIEW Cross-country comparson research has been conducted wdely n developed countres to nvestgate natonal dfferences n household energy consumpton patterns (Genjo et al., 25; Schpper and Ketoff, 983). Followng the footprnt of developed countres, analyses n Asan developng countres gradually rse snce the last decade. As mentoned by Naagam (26), n Asan countres, future large ncreases n energy consumpton appear unavodable, especally n tropcal regons (e.g., Indonesa and Malaysa), whose potental demand for coolng s extremely large. The exstng research on household energy consumpton n Asan developng countres shows that n the past 5 years, the dffuson of varous end-uses n households has contrbuted a lot to the ncrease of energy consumpton, le electrcty and gasolne (Genjo et al., 25; Murata et al., 28; Sadur et al., 27; Tyler, 996). However, the study n the context of Asa s very lmted, and one of the man reasons s the scarcty of the data. In order to provde detaled nformaton on energy consumpton, household level surveys are conducted whch are always organzed by natonal Bureau of Statstcs. These surveys can be dvded nto two types: consumer expendture (CEX) survey (e.g., USA, the Netherlands, Sweden, Japan and UK) and household energy consumpton survey (e.g., Canada and Japan). As we see, household level survey s very wdespread n developed countres, whle for developng countres t s lmted. Due to the mportant role of Asa on the global energy consumpton ncrease, t s necessary to carry out such nd of household energy consumpton surveys n Asa especally n developng countres, so as to derve more accurate nformaton for energy research and relevant polcy decsons. Under such consderaton, n ths study, we conduct a household energy consumpton survey n Toyo, Bejng, Jaarta, and Dhaa, cross-sector nformaton not only contanng n-home sector but also out-of-home sector referrng to personal travel are collected to 726

4 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 fully understand the energy consumpton pattern n households. Based on the valuable survey data, comparatve analyss s conducted on the aggregate level n ths study. Tll now, varous aggregate analyss whch deals wth energy consumpton at a natonal, regonal or sector level have been done (e.g., Ishda, 997; Lenzen et al., 26; Mura, 998; Shonal, 24). The results showed that resdental energy consumpton vares from house to house accordng to household characterstcs and lfestyles. However, these studes manly focus on the relatonshp of energy consumpton wth some soco-demographc attrbutes or resdental characterstcs, such as ncome, household sze, resdental locaton, etc. Later, researchers began to pay attenton to the household behavor when explanng energy consumpton. New forecastng models were developed to examne the nterrelated choce of car ownershp and energy consumpton, furthermore sgnfcant nfluence of end-use ownershp on household energy consumpton has been confrmed (e.g., Bn and Dowlatabad, 25; Chou et al., 29; We et al., 27). For nstance, Chou et al. (29) bult an ntegrated model to explan how the car ownershp nfluences the energy consumpton and emsson. However, these studes dd not consder the self-selecton effect whch exsts n the choce of end-use ownershp (ncludng prvate car and n-home electrc applances) and the household energy consumpton behavor smultaneously. Self-selecton s explaned as some unobserved subjectve factors that could mpact ndvdual s behavor, such as envronmental awareness, specal taste on drvng (Cao, 29). However, few studes have shed lght on the relatve mpacts of the car ownershp and self-selecton on energy consumpton behavor. From the concept of some lterature (Ajzen and Fshben, 98; Fransson and G rlng, 999; Nordlund and Garvll, 23), t s nown that atttudnal factors le envronmental awareness may stmulate the energy effcent behavor. People hgh n envronmental self-conscousness are motvated to care about the stuaton of the envronment and reject the energy ntensve behavors. In contrast, people low n envronmental self-conscousness who are less concerned about envronment mght be more lely to use energy ntensvely. Accordngly, t s very essental to consder the effect of self-selecton n the household energy consumpton behavor. In ths study, the causal effects of car ownershp and self-selecton on household energy consumpton behavor are explored and the relatve contrbuton rates of these two factors are separated. Emprcally, varous modelng approaches have been adopted to consder self-selecton effect n ndvdual s behavor (Cao et al., 29; Mohtaran and Cao, 28). In ths study, Hecman s latent ndex model (also called sample selecton model) s appled because the recent advances n sample selecton model mae t possble to separate the effects of the car ownershp and self-selecton on energy consumpton behavor (Hecman et al., 23). Accordngly, the model becomes approprate to address the central ueston of ths study, gven that many approaches are unable to uantfy the effect of the car ownershp on household energy consumpton behavor n the relatve sense (Mohtaran and Cao, 28). 3. METHODOLOGY A common approach to dealng wth selecton bas s to use a latent ndex model, whch relates the treatment to the lelhood of potental treatment outcomes. Ths approach s often called 727

5 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 Hecman s latent ndex model (Hecman, 976). In ths study, the treatment group denotes that households choose to own a car, whle the non-treatment group ndcates that households choose not to own a car. Household s pror selecton nto whether to own a car or not s frst decded, and then household energy consumpton s represented, condtonal on the pror selecton. More specfcally, households receve treatment (own a car) f the utlty of dong so s postve and do not receve treatment (do not own a car) f the utlty s negatve. Potental-outcome euatons (household energy consumpton) are specfed as follows: Consder a model of potental outcomes: Y Y x e, f D () x e, f D (2) where, Y and Y are the potental outcomes (refer to household energy consumpton n ths study) n two possble states (own a car ( D,.e., the recept of treatment) and do not own a car ( D,.e., no recept)) for household, respectvely; x and x are the th explanatory varables wth parameters and ; and are constant terms; e and e are error terms; D s a dummy varable, ndcatng where a car s owned or not, s defned below. Here, *, f D D (3) *, f D * D z (4) * D s a latent varable used to generate D, z s the th explanatory varable wth parameter, s a constant term and s an error term. A bnary probt model s developed to predct households car ownershp choce n ths study. Wth the above euatons, total household energy consumpton can be expressed as Y D Y (5) ( D ) Y Note that Y or Y s observed for each household, not both. The nformaton about varous Y Y. expected dfferences from the recept of treatment s denoted by To estmate the above latent ndex model, Hecman (976) proposed a two-step procedure, and Hecman et al. (2) descrbed the detaled procedure, whch s brefly summarzed as follows (Zhou and Kocelman, 28): Step: Estmate a bnary probt model to obtan for the treatment decson (own a car or not) and then use the estmated to calculate the selecton correcton terms (the 728

6 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 expectaton of the control varables). ( ( ) z E(,, z, D ) (6) ( z ) ( z ) E(,, z, D ) (7) z ) where, and are the probablty densty functon and cumulatve densty functon of a standard normal dstrbuton, respectvely. Step2. Treat the selecton correcton terms as new explanatory varables and add them nto euatons () and (2). Y Y ( ) z, x e f D (8) ( z ) ( ) z ( ), x e f D (9) ( z ) where, and are the parameters explanng the nfluence of selecton correcton terms on treatment outcomes (.e., household energy consumpton). To dsentangle the nfluences of the car ownershp tself and self-selecton, two mportant concepts artculated n Hecman et al. (2) are ntroduced here: average treatment effect (ATE) and the effect of treatment on the treated (TT). A treatment effect, loosely speang, s the value added or the dfference n outcome when a household undergoes treatment (own a car) relatve to not undergong treatment (not own a car). ATE represents the average ncrease n household energy consumpton of movng a randomly-selected household from a no car state to holdng a car state (treatment) wthout consderng the effect of self-selecton. Ths effect represents the drect nfluence of the car ownershp on energy consumpton behavor. TT s the expected outcome gan from the treatment for the group of households who select the treatment opton. In ths study, t ndcates the average addtonal energy consumpton of households who own a car by tang self-selecton nto account. TT represents the total nfluence of the car ownershp on energy consumpton behavor ncludng the self-selecton effect on n-home and out-of-home behavor. Therefore, the effect of self-selecton s the dfference between TT and ATE. In sample selecton models, pont estmates for ATE and TT can be derved usng the followng euatons (refer to Hecman et al. 2 for detaled dervaton). Let Y Y represent the ncrease n household energy consumpton (GJ) due to car ownershp change. The ATE condtonal on X x can be expressed as x ATE( x ) E[ X x ] x () 729

7 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 The uncondtonal estmate for ATE s ATE E[ ] ATE( X ) df( X ) n n ATE( x ) ( x x ) () n n Here, n s the sample sze. Condtonal on X x Z z, D, TT can be expressed as:, TT ( x, z, D ) E[ X x, Z z, D ] x x E( e e ( z) ) (2) Ths parameter s condtonal on the jont dstrbuton of X and Z, so the uncondtonal estmate s TT E[ D ] TT( X, Z, D ) df( X, Z D ) m n DTT( x, z, D ) ( ) z ( ) x x (3) ( z ) s s s where, m s the sample sze of the treatment group; corr( e, ) and s the standard s s s s devaton of e (s =, ); whch s the coeffcent for selecton correcton term ntroduced nto euatons () and (2). It s worth notng that although these estmates are derved under an assumpton of tr-varate normalty across the three error terms, a Monte Carlo experment showed that the estmates for ATE and TT have very low bas (a few percent) even when the data devate from the normalty assumpton (Cao, 29). 4. DATA Based on the standponts mentoned n the prevous secton, a household energy consumpton behavor survey was conducted n Toyo, Bejng, Jaarta, and Dhaa, respectvely, n February and March 29. The sample sze s about, households for each cty. Ths survey was desgned to collect the nformaton about the n-home/out-of-home expendtures and energy consumpton patterns of households. The uestonnare contents nclude the followng nformaton. () Attrbutes of representatve member: gender, age, educaton, and envronmental conscousness. (2) Household attrbutes: household sze, ncome, composton of members, housng area, dwellng type, and accessblty (dstance to bus/tran stop); these are used to explore nter-household varatons of energy consumpton. (3) Ownershp and usage of n-home applances (e.g., refrgerator, ar-condtoner, and washng 73

8 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 machne) and prvate vehcles (e.g., passenger car and motorcycle): attrbutes (e.g., type, sze, capacty) of applances and vehcles, freuency and/or duraton of usage per wee n dfferent seasons for applances and vehcles. (4) Energy consumpton: monthly energy consumpton or monetary expendture spent on electrcty, gas, water, erosene, gasolne, desel ol separately n dfferent seasons (four natural seasons n Toyo, Bejng, and Dhaa, whle dry and rany seasons n Jaarta), whch are converted to energy consumpton unt GJ so as to be utlzed n the followng analyss. Aggregate analyss of energy consumpton, household attrbutes, and end-use ownershp n treated and untreated households are frst carred out, from whch we can get the general features of the four megactes. Table shows the average values of annual energy consumpton, household attrbutes, and the ownershp of several nds of end-uses by dsentanglng the treated households and the untreated households n the four ctes. In order to remove outlers, both 2.5% of the maxmum and mnmum values for each data sample are excluded n the analyss. In Dhaa because the gas cost s fxed and there s no gasolne data, the energy consumpton analyss does not nclude these two parts. The aggregate statstcs reveals some smlarty and dfferences among these four ctes. Dfferences are as follows: ) Toyo has the hghest car ownershp share (nearly 6%), followed by Bejng and Jaarta (about 35%), and Dhaa s the least motorzed cty wth auto share less than %. 2) In Toyo and Jaarta, n-home energy consumpton, especally electrcty consumpton, regardless of total or per capta, s obvously larger than other two ctes, whereas, n Bejng and Jaarta more than half of energy consumpton comes from gasolne consumpton, that s to say, there are more heavy users of electrcty n Toyo, more heavy users of gasolne n Bejng, and more heavy users of both n Jaarta. 3) Attrbutng to the heavy use of gasolne n Bejng and Jaarta, the total energy consumpton n car ownng households are much hgher than no car households, whch s dfferent from the relatvely stable stuaton shown n Toyo. In other words, car ownershp s more senstve to household energy consumpton n developng ctes than n developed ctes. Smlarty s that for all these four ctes, the electrcty and gas consumpton are sgnfcantly dfferent between treated and untreated households, whch means the dfference n energy consumpton caused by car ownershp not only conssts n out-of-home energy consumpton, but also n n-home energy consumpton. Table Aggregaton statstcs of survey data Category Toyo Bejng Jaarta Dhaa Car ownershp share (%) Energy consumpton (own car) (GJ) Energy consumpton (no car) (GJ) Energy consumpton per capta (own car) Total energy consumpton Electrcty Gas Gasolne Total energy consumpton Electrcty Gas Gasolne Total energy consumpton Electrcty Gas Gasolne

9 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 Energy consumpton per capta (no car) Household attrbutes (own car) Household attrbutes (no car) End-use ownershp (own car) (%) End-use ownershp (no car) (%) Table Aggregaton statstcs of survey data (contnue) Category Toyo Bejng Jaarta Dhaa Total energy consumpton Electrcty Gas Gasolne Income (Thousand dollar) 85~9 ~2 8~9 5~6 Household sze(capta) Floor area (m 2 ) Dwellng structure, ron (%) Educaton bachelor (%) Resdental duraton (years) Access to transport staton (m) Income (Thousand dollar) 6~7 8~9 3~4 2~3 Household sze(capta) Floor area (m 2 ) Dwellng structure, ron (%) Educaton bachelor (%) Resdental duraton (years) Access to transport staton (m) Refrgerator (.2) 98 () 95 (.) 95 (.4) AC 99 (2.8) 96 (.6) 69 (.3) 45 (.8) Fan 72 (.9) 9 (2) (5.9) Washer (.) 95 (.9) 79 (.8).2(3) Be 82 (.74) 74 (.4) 52 (.8) Motorcycle 4 (.2) 8 (.) 8 () Refrgerator 99 (.) 93 (.9) 79 (.8) 4 (.5) AC 97 (.7) 87 (.3) 3 (.4) 5 (.) Fan 66 (.) 92 (.9) 92 (2.4) Washer 99 () 89 (.8) 58 (.6) () Be 69 (.2) 86 (.5) 37 (.5) Motorcycle 7 (.) 59 (.8) 6 (.2) Note: the number n parentheses s the mean ownershp of the applance or traffc nstrument. Household attrbutes of treated and untreated households n these four ctes vary a lot: the average household sze n Jaarta and Dhaa s larger than n Toyo and Bejng, whle the annual ncome s opposte; the average of household annual ncome, household sze, floor area, the percentage of hghest educaton level above bachelor are explctly larger n treated households than n untreated households. In Toyo the penetraton rates of most durable consumer goods le refrgerator, ar-condtoner, and clothes washer are already saturated. In contrast, n developng countres, t s lely that household energy consumpton wll contnue to rse attrbutable to prevalence of durable goods and the great populaton growth. Wth the ncreasng ncome, more and more households n developng countres wll lely ncrease the applance ownershp and energy use over the comng decade, especally for Dhaa, because of the lowest penetraton of most applances. Another fndng s that the motorcycle ownershp rate s very hgh n Jaarta and the energy use of motorcycle accounts for nearly 5% of the total energy consumpton n the households wthout a car, whch s a typcal phenomenon n Southeast Asan developng countres (e.g., Vetnam, 732

10 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 Malaysa). Besdes the trats mentoned above, there s a smlarty among these four ctes that s the ownershp rate of energy ntensve end-uses are hgher n treated households than untreated households. And ths mght be one reason to explan the dfference of energy consumpton between these two types of households n vared ctes. Based on the aggregate analyss, we can now that households observed recevng treatment (ownng a car or cars) often present dfferent characterstcs from those not recevng the treatment n each cty. Conseuently, clarfyng the nfluental factors for treated and untreated households s essental to understand relatonshp of car ownershp and household energy consumpton behavor. 5. MODEL ESTIMATION RESULTS 5. Results of Treatment Selecton Model Table 2 Estmaton results of car ownershp model (treatment selecton model) Explanatory varable Toyo Bejng Jaarta Dhaa Constant term ** ** ** ** Log(Income) **.86 **.384 * Household sze.43 **.2 **.53 ** -.5 Educaton level.64 **.24 **.47 *.85 Dstance to bus/subway stop.52.4 *.24 * -.2 Car lcense ownershp.674 ** ** Number of Observatons Intal Log-Lelhood Converged Log-Lelhood Rho-suared Note: **. sgnfcant at the % level; *. sgnfcant at the 5% level. A bnary probt model was employed to descrbe the choce of whether to buy a car as well as to control the selecton bas n treated and untreated households (.e., euatons (3) and (4)). The explanatory varables nclude household annual ncome, household sze, hghest educaton level (whether above bachelor), accessblty (dstance to bus/ subway staton), and car lcense ownershp. The model estmaton results are shown n Table 2. It s revealed that the sgnfcant factors dffer across ctes: n Toyo, household sze, educaton level, and car lcense ownershp sgnfcantly affect car ownershp choce, whle n Jaarta and Bejng, besdes household sze and educaton level, ncome and accessblty are also valdated to be sgnfcant. In Dhaa, only ncome and car lcense ownershp wor. The estmaton results mentoned above mght be nterpreted as follows: n Toyo, the hgh average ncome level maes buyng a car for every household more easly than other ctes, n other words, ncome s no longer a man factor to decde whether to buy a car n developed ctes. In addton, t mght because of the good accessblty to transport staton n Toyo (.e., average.5m, varance of.2m compared to Bejng 6.m, Jaarta 4m, Dhaa m), the factor Dstance to bus/subway stop s found not sgnfcant here. Due to the vared reurements of larger famles, t s reasonable that household sze postvely mpacts the probablty of ownng a car. Hgher educaton level s always related to a better job, conseuently resultng n a hgher probablty to have a car. Based on the 733

11 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 coeffcent estmates of ths probt model, the sample correcton terms are calculated based on euatons (6) and (7), and used to estmate the followng treatment outcome models (.e., household energy consumpton models). 5.2 Results of Treatment Outcome Models Treatment outcome models (.e., euatons (8) and (9)) for household energy consumpton were estmated, correspondng to the two treatment-specfc groups (.e., those holdng a car, versus those wth no car). For Toyo, Bejng and Jaarta, the dependent varable s total household energy consumpton ncludng n-home (electrcty, gas) and out-of-home (gasolne) consumpton, whle for Dhaa, t s electrcty consumpton (GJ) due to the lac of data. Explanatory varables consst of household attrbutes, end-use ownershp, and the selecton correcton term. Prelmnary analyss results suggest that educaton level, ownershp of frdge and washer are statstcally nsgnfcant n both euatons for these four ctes, therefore, these are not ncluded n the fnal model. Snce calculaton of Hecman s treatment parameters reures the same number of explanatory varables n each of the two euatons, varables that are statstcally nsgnfcant n just one of the euatons are retaned n both models, and n order to do the comparatve analyss among four ctes, the explanatory varables are fxed the same for each cty. Estmaton results are shown n Table 3. Table 3 Estmaton results of household energy consumpton models (treatment outcome models) Toyo Bejng Jaarta Dhaa Dependent varable Total energy Total energy Total energy Electrcty Explanatory varable Treatment (Car ownng state) Constant ** Log(Income) **.76 * ** Household sze ** 4.76 ** **.485 ** Dwellng structure * ** Resdental years.49.3 ** Floor area -.56 * -.7 *.8.45 ** Ownershp of AC.69 * **.55 Correcton term ** *.48 Number of Observatons Rho-suared Non treatment (No car state) Constant ** 4.95 ** **.23 Log(Income).49 ** **.29 ** Household sze 7.57 **.94 ** 3.89 **.992 ** Dwellng structure -.53 * *.5 * Resdental years * Floor area ** Ownershp of AC **.487 ** 9.73 ** -.3 Correcton term.525 * 3.97 * Number of Observatons Rho-suared Note: **. sgnfcant at the % level; *. sgnfcant at the 5% level. 734

12 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 The results n Table 3 show that the statstcally sgnfcant varables dffer among ctes, furthermore, the sgnfcant factors and ther nfluental effects vary between treated and untreated households n all ctes. The most obvous dfference s that n Toyo, ncome negatvely mpacts the energy consumpton n treated households, whle opposte n untreated households. Ths status can be explaned by the well-nown Envronmental Kuznets Curve (Lopez, 994): ncome and envronmental emssons are under a relaton of nverted U-shaped curve. In other words, envronmental emssons ncrease wth the rsng ncome at frst, but when the ncome reaches a certan level, envronmental emssons turn to decrease. Such decreasng trend mght be caused by the mprovement of technologcal effcency, the advance of envronmental awareness, and other changes of the socety. For these four ctes, household sze s postvely correlated to household energy consumpton regardless of the household type. The ownershp of ar condtoner also has a postve nfluence on energy consumpton n Toyo, Bejng and Jaarta. The selecton correcton term s proved to sgnfcantly affect the household energy consumpton n the car ownng households n Bejng and Jaarta as well as no car households n Toyo and Bejng. Table 4 Partal utlty results Toyo Bejng Jaarta Dhaa Treatment (Car ownng state) Log(Income) Household sze Dwellng structure Resdental years Floor area Ownershp of AC Correcton term Non treatment (No car state) Log(Income) Household sze Dwellng structure Resdental years Floor area Ownershp of AC Correcton term In order to clarfy the most nfluental factors to household energy consumpton n Toyo, Bejng, Jaarta, and Dhaa, the partal utlty (absolute value) s calculated by multplyng the coeffcent and the mean of each varable together (see Table 4). The partal utlty can be understood as a contrbuton of each varable to the dependent varable. Based on ths ndex, the most nfluental factors n treated households are dentfed: household sze n Toyo and Bejng, ncome n Jaarta and Dhaa, respectvely. Whle the top nfluental factors n untreated households are: household sze n Toyo and Dhaa, ncome n Bejng and Jaarta. Overall, the top two nfluental factors are ncome and household sze no matter n treated or untreated households, whch s consstent wth the prevous research (Moll et al., 25; O'Nell and Chen, 22; Pachaur, 24). The partal utlty of selecton correcton term n Bejng and Jaarta s relatvely larger than other two ctes, that s to say, the ncrease of household energy consumpton caused by the dfference of subjectve psychologcal varables, such as the 735

13 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 envronmental awareness, s greater n Bejng and Jaarta. 5.3 Results of Treatment Effects Table 5 shows the treatment parameters and the self-selecton effects. The ATE of Toyo s estmated to be 3.5 GJ per year, whch means a randomly selected household s expect to ncrease ts energy consumpton by 3.5 GJ per year after buyng a car, as compared to no car state. Gven the average observed total household energy consumpton 56.5 GJ per year n Toyo, 3.5 GJ represents more than 23% ncrease n yearly energy consumpton. Lewse, the ATE of Bejng s GJ, whch means more than % ncrease n yearly energy consumpton compared to the average observed GJ, and for Jaarta, the ATE s 49.3, amountng to 72.8% ncrease. Due to the lac of data, here the ATE of Dhaa reflects that a randomly selected household s expect to ncrease ts electrcty consumpton by.67 GJ per year after buyng a car as compared to no car state. Ths result shows that the ownershp of car not only leads to dfferent gasolne consumpton n each household, but also changes the n-home energy consumpton, n other words, the nterrelatonshp between n-home and out-of-home energy consumpton behavor s confrmed. However, due to the small sample sze of treatment group n Dhaa, ths concluson should be further valdated by usng other cty s data n the next step. Table 5 Treatment parameters and self-selecton effect Treatment Parameters Toyo Bejng Jaarta Dhaa ATE TT ATE/TT 9.3% 86.59% 78.3% 69.7% Self-selecton 9.87% 3.4% 2.69% 3.93% The TT was estmated to be 4.59 GJ n Toyo, suggestng that a household ownng a car can be expected to exhbt 4.59 more yearly energy consumpton (GJ) than havng no car state, ceters parbus. Based on the sze of these two effects (ATE and TT), the mpacts of the car ownershp on annual household energy consumpton (.e., the GJ ncrease due to ownng a car, rather than no car state) s estmated to be 9.3% of the as-observed dfferences n treated and untreated households. Ths mples that the total effect of self-selecton ncludng on n-home and out-of-home energy consumpton behavor accounts for nearly % of observed energy consumpton (GJ) dfferences across households ownng a car versus no car households. Essentally, f all no car households buy a car may be expected to yeld hgher energy consumpton ncrease than analysts may perceve at frst glance. Lewse, the TT s estmated to be GJ n Bejng, GJ n Jaarta, and.9 GJ n Dhaa. The mpacts of car ownershp on annual household energy consumpton can be computed: 86.59% n Bejng, 78.3 % n Jaarta, and 69.7% n Dhaa, whch nfers that the self-selecton effect accounts for 3.4% n Bejng, 2.69% n Jaarta, and 3.93% n Dhaa. Ths result reveals that the greater maturty of economc development of a cty (reflected by average ncome level derved from the survey data), the smaller effect of self-selecton on household energy consumpton behavor. In developed ctes, because of the overall relatvely hgher envronmental awareness, the household energy consumpton dfference caused by atttudnal factors s much less sgnfcant than n developng ctes. 736

14 Journal of the Eastern Asa Socety for Transportaton Studes, Vol.9, 2 6. CONCLUSION It s expected that the household energy consumpton as well as the effects of ther nfluental factors vary wth the economc development level of dfferent ctes. In order to understand the energy consumpton patterns of dfferent ctes, as well as examne the effects of car ownershp and self-selecton on household energy consumpton behavor, ths paper presents a comparatve analyss of household energy consumpton across an array of household attrbutes and end-uses owned by households n Toyo, Bejng, Jaarta and Dhaa, the four representatve megactes n Asan regon. For the sae of dsentanglng the effects of car ownershp and self-selecton on household energy consumpton behavor, Hecman s latent ndex model s appled here for each megacty to explore the causal effect of car ownershp on household energy consumpton behavor and ts relatve contrbuton to the total nfluence by usng the data we collected from a uestonnare survey of household energy consumpton n these four megactes n 29. Moreover, the effect of the car ownershp tself and the effect of self-selecton are separated. Three man conclusons can be derved from the aggregaton analyss and the model estmaton results. Frst, the statstcally sgnfcant varables to household energy consumpton behavor vary among ctes; furthermore, n the same cty the nfluental factors are dfferent wthn car ownng households and no car households. Whereas, the top two nfluental factors n Toyo, Bejng, Jaarta, and Dhaa, are all ncome and household sze. Second, t s found that the effect of car ownershp tself on the ncrease of household energy consumpton accounts for 9.3% n Toyo, 86.59% n Bejng, 78.3% n Jaarta, and 69.7% n Dhaa. Ths consderable nfluence n these four ctes provdes a supportve evdence for the truth that changes n car ownershp stmulate great changes n household energy consumpton behavor. Moreover, the effect of self-selecton on the ncrease of household energy consumpton accounts for 9.87% n Toyo, 3.4% n Bejng, 2.69% n Jaarta, and 3.93% n Dhaa. Ths result mples that the greater maturty of economc development of a cty, the smaller effect of self-selecton on household energy consumpton behavor. In addton, due to the exstence of self-selecton, the car ownershp and household energy use should be analyzed together nstead of separately treated, furthermore, the role of soft polces such as popularzng hgh level educaton, renforcng propagaton of envronmental protecton, etc. are emphaszed n both developed ctes and developng ctes, especally the latter. Overall, comparatve results show that although both the car ownershp and self-selecton nfluence household energy consumpton behavor, the car ownershp tends to play a domnant role no matter n whch cty. Fnally, t s at least confrmed that there s nteracton between n-home and out-of-home energy consumpton behavor based on the result of Dhaa. The change of car ownershp not only leads to dfferent gasolne consumpton n each household, but also alters the n-home energy usage (based on the result of Dhaa). Therefore, nstead of dervng future total energy needs by smply summng up the forecastng of n-home demand and out-of-home demand as exstng studes do, a jont representaton of n-home and out-of-home energy consumpton behavor should be consdered so as to properly predct the energy demand. Havng examned the energy consumpton pattern n each cty by consderng car ownershp and self-selecton, more accurate predcton of energy demand can be acheved, furthermore, concrete 737

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