|Unit||Vol. Index 2015=100, NSA|
|Adjustments||Not Seasonally Adjusted|
Sales index in services
According to the CZ-NACE, units with predominating activities in sale, maintenance and repair of motor vehicles; retail trade of automotive fuel; wholesale trade and commission trade; retail trade except of motor vehicles, repair of personal and household goods; hotels and restaurants; transport and communication; real estate, renting of machinery and equipment; computer activities; other business activities and other personal service activities are classified in services. The sales index indicator serves for the evaluation, analyses of short-term development and possible predictions of future development in services.
Methodology - monthly sales indices in trade, hotels and restaurants
Formation of the selective sample
Reporting units are selected from the Business Register. Sample strata are defined by the size of the unit (number of employees) and principal activity (usually a 3-digit level CZ-NACE category), the sample is taken for each strata separately. Included in this selection are all units with 50 or more employees. Proportional sampling is used in the other groups of enterprises. It is possible to apply the proportional sampling only in a situation when relevant information (in this case sales) exists for all units in the basic sample. The probability of including the unit in to the sample is directly proportional to the share of its sales on total sales of all units in strata. It is therefore ensured that units with above the average sales have a bigger probability to be included in the sample than units with lower sales and hence they are not exposed to unnecessary administrative burden. The importance of small enterprises however is not undervalued as the products of weights of individual enterprises and their sales are within the strata equal.
The sample strata are subjected to a so-called rotation i.e. partial replacement of part of the sample, with the aim to update the set of units to which the questionnaires are send and to retain the stability and hence the comparability with data produced in preceding years. That usually means that enterprises, having been selected at random, remain in the sample for two successive years; then they are excluded from the sample and replaced by new reporting units. The criterion for including all units into the sample is applied during the observed year; basic and selective samples are hence updated regularly with new units, which correspond with this criterion.
Description of indicators observed
Monthly questionnaire covers sales of own products, goods and services in the reference month. Sales are recorded both including VAT and not including VAT. Units report also sales of results of activities that are not subject to VAT (e.g. exports).
Initial questionnaire, which is send to units included in the selection for the first time contains information on whether the reporting unit is active, information about the principal activity of the unit, and sales in individual months of the preceding year.
Description of calculating the sales index
The development of divisions is represented by the sales index with VAT depending on the fact that the price index used for the recalculation of sales into constant prices includes VAT.
In wholesale the index at constant prices is not calculated because the wholesale prices are not observed. Therefore the index is released at current prices without VAT.
Year-on-year sales indices at current prices are calculated for individual months for each CZ-NACE lowest aggregate (e.g. CZ-NACE 52.11 or 52.41-52.43). The y-o-y price deflators for individual months of the current year are used for these CZ-NACE categories; price deflators of individual months related to the year’s average are used for the base year. Absolute values of monthly sales at current prices for the lowest CZ-NACE aggregates are converted to the price level of 2000 using the method of chaining deflators. By the summation of the lowest aggregates of absolute sales values at constant prices in individual months we get higher sale aggregates from which we calculate y-o-y sale indices at constant prices. The sum of monthly sales of aggregated CZ-NACE categories at current prices for 2000 is equal to the sum of their sales at constant prices.
Comparability with other surveys in terms of methodology
The results of monthly surveys may differ from the results based on quarterly or annual surveys, which are designed to serve the estimate of the total volume of sales, not only index.
Discrepancies may also arise from different samples in some CZ-NACE activities where the volumes of sales are largely dispersed.
Methodology of indicators
Retroactive corrections, revisions
Along with the processing of February data, revision of January data will be carried out. In case of requirements, data revisions are carried out along with the processing of the first month that follows the publication of quarterly data e.g. along with the processing of April data, data for January-March are revised. Final data are published following the processing of all of the months of the observed year, in June of the following year at the latest.
Along with the processing of April 2008 data, the base for computing base indices of seasonally adjusted data and trend was methodologically changed.
The area of short-term statistics in the European Union is guided by EU Regulation No 1165/98 and 1158/2005 on short-term statistics. Under this Regulation, EU member states are obliged to provide information on retail turnover on a monthly basis (current and constant prices) and on turnover in selected services every quarter (current prices). The indicator is comparable in terms of methodology, with the following difference: with regard to long time series, retail turnover in the Czech Republic is published incl. VAT, while Regulation No 1165/98 requires retail turnover not incl. VAT. The CZSO has both types of the retail turnover indicator available; with regard to traditional users and with respect to the construction of deflators, the CZSO publishes the retail sales index incl. VAT.
The size of sales during a year in some industries is strongly affected by seasons (e.g. Christmas shopping in retail trade, tourist season in services related to tourism and the like). In order to find out long-term trends and to be able to compare month – on – month or quarter – on quarter development, the CZSO produces seasonally adjusted data, when the part of sales caused by a seasonal swing is separated from the original “rough” series, using a mathematical model. Seasonally adjusted data are comparable not only between years, but also between individual months (quarters).
Method TRAMO/SEAT recommended by Eurostat is used for seasonal adjustment. Program application DEMETRA is employed in the CZSO. Seasonal adjustment is made at the lowest level (usually 3-digits CZ-NACE); the so-called indirect method (sum of seasonally adjusted sales of 3-digit CZ-NACE items) is used for calculating seasonally adjusted aggregates (CZ-NACE 2-digit level, services total, etc).
For more information please visit https://www.czso.cz/csu/czso/retail_trade_hotels_and_restaurants_time_series.