CONSUMER PRICE INDEX METHODOLOGY (Updated February 2018)

Transcription

1 CONSUMER PRCE NDEX METHODOLOGY (Updated February 208). Purpose, nature and use The purpose s to obtan country representatve data for the prces of goods and servces and to compute overall and group ndces of consumer prces. The consumer prce ndex (CP) s a measure of the general relatve change of the prces of goods and servces used by households for prvate (non-producton) consumpton. t s defned as the pure prce change ndex. The total consumer prce ndex summarzes the ndvdual prce ndces of the observed goods and servces. The CP s the chaned Laspeyres-type ndex whch reflects the pure prce change.e. the ndex reflects only the change n prces between the current and the base perod. The CP does not measure the cost of lvng and t s not a cost of lvng ndex. The consumer prce ndex s appled n three man areas as: Macroeconomc ndcator - as offcal measure of nflaton n Bulgara; Deflator of the values of ndcators, whch do not have ther own prce measure; Tool for possble ndexaton of salares, pensons and other ncomes from the Government when needed. 2. Structure of the CP The structure of the CP s a natonal verson of the ECOCOP classfcaton the European Classfcaton of ndvdual Consumpton Accordng to Purpose, accordng Regulaton (EU) 206/792 of May 206 of the European Parlament and of the Councl. t s herarchcal and s bult on fve levels: Dvson; Group; Class; Subclasses; Elementary aggregate. The frst four levels cover the structure of ECOCOP. The natonal CP covers all subclasses whch have a weght accountng for more than /000 of total weght (.e. 2 dvsons, 42 groups, 97 classes and 207 subclasses). The lowest level s natonal and defnes the expendtures for ndvdual consumpton n the respectve elementary aggregate s groups. The groupng of goods and servces n both classfcatons ECOCOP for the needs of harmonzed CP, and for the needs of household budgets survey ensures coordnated usage of ECOCOP as the statstcal standard. The natonal CP for the year 208 comprses 8.8% of the total fnal monetary expendtures n Sample Coverage CP complaton s based on four samples: Consumer basket - sample of goods and servces, offered at the consumer market; Geographc coverage - sample of settlements, where observaton ponts wll be sampled; Regulaton (EU) 206/792 of the European Parlament and of the Councl of May 206 on harmonsed ndces of consumer prces and the house prce ndex, and repealng Councl Regulaton (EC) No 2494/95 (ОJ L 35, ,p.)

2 Observaton ponts - sample of stores, shops, restaurants, cafes, etc. n the sample of settlements; Target number of prces set of prces of goods and servces to be prced at the sampled observaton ponts. 3.. Consumer basket The consumer basket ncludes goods and servces, whch represent the fnal consumpton of households. The followng prncples are observed: The goods and servces to be prced n the CP should be a fxed (unchanged) seres of goods and servces durng the year, whch has to reflect the average change n prces for all goods and servces and has to correspond to the structure of households consumpton; A correspondence wth the defntons n the System of Natonal Accounts should exst n respect of prvate consumpton and ts coverage; Consstency wth the classfcaton of goods and servces used n nternatonal comparsons of prces n accordance wth the Programme for European Comparsons (PEC) should exst; Goods and servces should nclude publc utltes wth tarff prces; Goods traded between households, and goods bought n nsgnfcant quanttes, should be excluded. The prces of specally selected representatve products (sample of goods and servces representatves, so called consumer basket ) are collected. Selecton and specfcaton of the products s done jontly by staff n central offce and by prce collectors n regonal statstcal offces. Procedures for specfyng the goods and servces representatves can be descrbed as follows: defnton of an ntal product samplng framework usng HBS results; use of alternatve data sources for the defnton of the exact characterstcs of the sampled products (admnstratve data, prvately-owned data bases, etc.), n addton to HBS data, where possble; use of prce collectors feld experence when nformaton from the HBS and other data sources s not enough for the defnton and specfcaton of the sampled products; extracton of the sample usng purposve samplng technques. The specfcatons for ndvdual goods/servces are more or less detaled; ndcatng sze, unt, materals, model, brand characterstcs, etc. How tght or loose the specfcatons wll be depends on the nature of the product. f a product has many characterstcs could affect ts prce, the specfcaton s more exact. There are detaled specfcaton n case of cars, medcnes, fuels and some foods and servces. For the most of the products looser specfcatons are used. The specfc varety of the good/servce (reference product-offer), whose prce wll be collected n the sampled outlet, s selected by prce collectors. They are nstructed to pck the typcal product varety: whch s the most sold n the sampled outlet; and; whch meets as close as possble the specfcaton of the product. At the end of each year durng the annual CP revson several letters wth nstructons for the prce collectors are sent to RSOs. The procedures for selectng the partcular product n outlets are covered n them. The ssue s also dscussed on the semnars/workshops wth prce collectors, whch take place regularly. The consumer basket for the year 208 conssts of 730 goods and servces, dvded nto four basc groups: Foods - 69; Non-foods - 349; 2

3 Caterng - 5; Servces - 6. These goods and servces are grouped nto 2 basc dvsons n accordance wth the ECOCOP classfcaton: Food and non-alcoholc beverages; Alcoholc beverages and tobacco; Clothng and footwear; Housng, water, electrcty, gas and other fuels; Furnshngs, household equpment and routne household mantenance; Health; Transport; Communcatons; Recreaton and culture; Educaton; Hotels, cafes and restaurants; Mscellaneous goods and servces Geographc coverage The sample of settlements ncludes settlements n 27 dstrct centers. Over 50% of the populatons of the country lve n the sampled settlements and over 65% of the sales are made n them Observaton ponts The number and the structure of the observed market ponts are selected n a way that can assure the optmum number of prces collected, whch are suffcent to represent natonal prces for any group of goods and servces n the consumer basket. The sample ncludes outlets, whch: have a large volume of retal sales; supply a varety of goods, representatve of the relevant elementary aggregates n the consumer basket. The man types of retal trade are covered, ncludng the bggest outlets such as: supermarkets, general and specalzed stores, cooperatve markets. The selecton s made by prces collectors and s confrmed by the drector of the respectve regonal statstcal offce. There are above observaton ponts for the year Target number of prces n 208 the planned monthly number of observatons s , dstrbuted among the four basc groups as follows: Foods ; Non-foods ; Caterng ; Servces Organzaton of prce collecton 3

4 The target number of prces for every good and servce n the consumer basket s fxed. The prce collecton perod s from st to 28th of each month on a schedule, whch s drawn up n the relatve regonal statstcal offce and s confrmed by ts drector. Prces are collected by qualfed specalsts, employed n the regonal statstcal offces. Prces are recorded n specal notebooks or by electronc devces. 5. Calculaton of Consumer Prce ndex Calculaton of the CP s based on the followng nformaton: Base prces annual average prces n the prevous year for every tem n the consumer basket; Base weghts calculated from the monetary expendtures of households n the prevous year. Base prces and base weghts are updated every year. There are four stages n the calculaton procedure: A. Calculaton of mputed prces The ndces for all elementary aggregates are compled and where necessary mssng prces are mputed usng the change n a matched sample of average prces. Where a matched sample s not avalable, prces are mputed wth the help of an upper-level group ndex. The ndex t/ t, wth whch the mputaton s done, comples as: m Pt t/ t = m, = Pt S S t P t denotes avalable prces n perod t; P t - avalable (real and mputed) prces n perod t-; S t - set of avalable prces n perod t; S t - set of avalable prces n perod t-; m - number of prces, whch belong to sub-set S B. Calculaton of the aggregate CP t t St. The average natonal prce for every good or servce n the consumer basket s compled as the geometrc mean of all prces (real and mputed): P n = n t P t =, P t denotes natonal prce for the current month; P t - prce of -th tem; n - number of recorded and mputed prces. C. Calculaton of base ndces for the current month t The base ndex for elementary aggregate (5th level) s calculated as the rato of geometrc mean prces, that are part of a gven aggregate: 4

5 t / b, b Pt = n S t P S t denotes the set of all prces (real and mputed) n perod t; P t - -th current prce for an elementary aggregate; P b - -th base prce for an elementary aggregate; n - number of prces n an elementary aggregate. Base ndces for the groups of 4th, 3rd, 2nd and st level are compled as Laspeyres-type ndces: t / b( m) = n = t / b( m+ ). W( m+ ) n = W ( m+ ), m s the herarchcal level (m=4 for group of goods, m=3 - class, m=2 - group, m= - dvson and m=0 - overall CP); n - number of groups from (m+)-th herarchcal level, gong nto the group from m-th herarchcal level; W (m+) - base weghts. D. Chan ndces Chan ndces durng one year for all levels are compled as the rato of the base ndces for the current month and the relatve base ndces for the prevous month. t / t ( m) = t / b ( m) t / b ( m) The consumer prce ndex s a chaned Laspeyres-type ndex. The chan ndex for January of the current year takng December of the prevous year as 00 (refers to the general ndex and partcularly to any herarchcal level) comples as: JJJ208 = JJJ DDD207 DDD JJJ s the base ndex for January 208 wth 207 as prce and weght reference; DDD amendng base ndex, defnng the change of prces n December 207 takng the annual average prces n 207 as 00, weghted wth the monetary expendtures n Treatment of the qualty changes of the observed products When the CP s calculated, t s mportant to be prced the products wth unchangeable qualty, because the change n prces should reflect only pure prce changes not changes due to change n the qualty of the observed products. The most nfluental methods wth dealng wth qualty change of products are: Annual overlap. For many of the products new samples are drawn each year durng the annual revson of consumer basket. December s used as lnkng month and then the dual prce 5

6 collecton s done the prces are collected both for the old and for the new sample. Qualty dfferences between these two samples are then elmnated by overlap method called annual overlap. Drect comparson. Prce collectors are nstructed to measure the prce for the same varety throughout the year and f the varety dsappears permanently from the market, they should choose another one wth the most smlar qualty. n these cases, drect comparson method s appled, because of the mnor dfference n qualty between the old and the new varety. mplct qualty adjustment methods. n some partcular cases, the second approach s not applcable, due to the fact that qualty dfference between old and new product s sgnfcant, and mplct qualty adjustment methods are appled: (a) overlap s used when the prces of both products are avalable n the same tme perod; (b) brdged overlap s used when they are not avalable; and (c) opton cost. Qualty adjustment procedures are done centrally by the staff n central offce. At regonal level, prce collectors do not make any qualty adjustments; they are only nstructed to report to central offce for the all cases of consderable qualty changes of the replacement products. 7. Publcty and transparency 7.. Announcement of results The CP data s publshed together wth CP data to a strct, pre-announced tmetable n general 2 and 6 calendar days after the month n a queston. The CP data whch s released each month covers the monthly ndces and rates of change, annual ndces, annual average ndces and ndces for the current month compared to December of the prevous year. The press release ncludes also data for prce changes of the basc consumer groups: foods, non-foods, servces and caterng Publcatons Statstcal Yearbook of the Republc of Bulgara, Chapter Prces ; Statstcal Reference Book, Chapter Prces - annual publcaton of NS; Bulgara - annual brochure of NS; Key ndcators for Bulgara ; Consumer Prce ndex and nflaton - Answers to the Most Frequently Asked Questons - brochure Electronc access The NS has a WEB-page n the nternet. The address s: Basc data for consumer prce ndces, the entre methodology of CP complaton as well as the consumer basket can be found there. 6