English / Česky
ISPV Results  > >Methodology

Methodology

On this page, you can find detailed information on the methodology of the ISPV survey. Attention is further paid in particular to

Wage and Salary Spheres

Results of the ISPV survey are divided into two spheres. The wage sphere includes economic subjects who provide remuneration in the form of wages pursuant to Section 109 (2) of Act No. 262/2006 Coll., the Labour Code, as amended. Economic subjects belonging to the salary sphere provide remuneration in the form of salaries pursuant to Section 109 (3) of Act No. 262/2006 Coll., the Labour Code, as amended. Until 2010, the wage sphere was called the business sphere and the salary sphere was called the non-business sphere. The reason of change is described in detail here.

Population and Sample Design in the Wage Sphere

The population of the wage sphere (ISPV-MZS) is a set of active economic subjects defined on the basis of the Business Register (RES) maintained by the Czech Statistical Office (CZSO) who provide remuneration in the form of wages pursuant to Section 109 (2) of Act No. 262/2006 Coll., the Labour Code, as amended. RES is described in detail on the website of the CZSO (www.czso.cz).

The ISPV-MZS results are based on the simple stratified random sampling without replacement. Sampling units are the economic subjects who are, in case of being selected, subject to the reporting obligation. Statistical units are the employees who are bearers of the monitored statistic features. The population is divided into subpopulations (strata) by:

  • institutional sectors,
  • size categories,
  • economic activity groups,
  • districts (regions).

In individual subpopulations that emerged by stratification of the population, the sampling fraction of economic subjects is set. The sample is made from institutional sectors used in the national accounts, i.e. from sectors of non-financial corporations, financial corporations, general government, households (own-account workers) and non-profit institutions serving households.

In the largest sectors, i.e. in the non-financial corporations and households - subjects with 250 and more employees are all included in the survey (sample probability equals 1). Smaller subjects with up to 249 employees are sampled in individual strata by systematic random sampling with unequal probabilities without replacement. Selection probabilities differ depending on the size of the subject and their level is determined by the sampling ratio specified in Table 1. Sampling of economic subjects with 1 to 9 employees is carried out every 4 years; the last selection took place for the year 2010. Within the sample of economic subjects with 10 to 249 employees, a rotating panel method is used. The rotation period is nine years, i.e. full rotation is achieved in nine years.

Table 1: Size categories for stratification
Category Number of employees Sampling ratio [%]
1 1 to 9 1.2
2 10 to 49 4.5
3 50 to 249 15
4 250 and more 100

Economic subjects with 50 and more employees in the sector of financial corporations and general government and subjects with 65 and more employees in the sector of non-profit institutions are all included (sample probability equals 1). Smaller subjects from the above mentioned sectors are subject to the probability sample.

Economic subjects are sampled from 6 basic economic activity groups: agriculture, industry, construction, trade, market services and other services. Within each basic group, more detailed strata are identified by cluster analysis on the basis of similarity of the wage level and the structure of occupations. As for the selection of units, a district means a region within the meaning of the Constitutional Act No. 347/1997 Coll., as amended.

The ISPV-MZS statistical survey for the first half-year of 2011 included 4,256 economic subjects representing 1,348,000 employees.

You can find the structure of the ISPV-MZS sample as far as sectors of economic activity and regions are concerned in the annex to ISPV publications publications for the wage sphere in PDF format.

Survey Concept in the Salary Sphere

The population of the ISPV salary sphere (ISPV-PLS) is a set of economic subjects defined by the Automated Budget Information System (ARIS) administered by the Ministry of Finance. ARIS includes information from the accounting and financial reporting of the organization units of the state, state budget chapters, state-funded institutions, state funds, territorial self-administration units and state-funded institutions in the Czech Republic (see http://wwwinfo.mfcr.cz/aris). Economic subjects belonging to the salary sphere provide remuneration in the form of salary pursuant to Section 109 (3) of Act No. 262/2006 Coll., the Labour Code, as amended. The ISPV statistical survey for the salary sphere uses the data from the Salary Information System (ISP) run by the Ministry of Finance (see www.mfcr.cz/isp).

The ISPV-PLS survey for the first half-year of 2011 represents 13,704 economic subjects with total employment of 560,000 employees. The data complying with ISPV-PLS checks are included. As for the sectors of economic activity according to the classification CZ-NACE, the salary sphere is represented in particular by three sectors of economic activity, namely by the public administration, education and health and social care. From the geographical point of view, the ISPV-PLS covers the Czech Republic. Detailed information about the structure of the ISPV-PLS is included in the annex to ISPV publications for the salary sphere in PDF format.

Classifications

In each sphere, ISPV results are broken down by social-economic characteristics of employees (e.g. occupation according to the classification CZ-ISCO, age, sex, education, etc.) or by characteristics of economic subjects (e.g. sector of economic activity according to the classification CZ-NACE).

Periodicity and Contents of Individual Publications

In the wage sphere, the survey is carried out under the name Quarterly Survey of Average Earnings and is included in the Programme of Statistical Surveys maintained by the CZSO and published every year as a Decree on the Programme of Statistical Surveys in the Collection of Laws. Basic data about wages, working hours and number of employees for the whole economic subject (see the record on the economic subject, the so-called MI file) are surveyed quarterly. In addition, detailed information on wages and working hours of individual employees (see the record on employment, the so-called MP file) are surveyed every half-year.

The data source of the salary sphere is the Salary Information System (ISP) administered by the Ministry of Finance that is used each half year.

Since 2011, a publication about wages and working hours accroding to the sector of economic activity is issued for each quarter. For each even quarter, this publication is extended by information about hourly earnings of employees. Publications for the wage and salary spheres including data about wages and working hours according to detailed social-economic variables, in particular by individual occupations, are issued for the first half year and for the whole year. Once a year, ISPV is supplemented by the Regional Earnings Statistics (RSCP), which provides a summary of the earnings level and worked hours by occupations in individual regions of the Czech Republic.

Until 2010, a detailed publication for the wage sphere (called the business sphere until 2010) was issued for each quarter and the same tables were issued also for individual regions within the RSCP. Each even quarter, a detailed publication was issued for the salary sphere (called the non-business sphere until 2010) and the same tables were issued also for individual regions within the RSCP. As far as hourly earnings are concerned, the time period corresponded to a specific quarter. As for gross monthly wage and working hours, the time period corresponded to the period from the beginning of the year until the quarter end, for which the statistical survey was carried out (i.e. for Q1, Q1-Q2, Q1-Q3 and Q1-Q4 of the relevant year).

Main ISPV Variables

The most important variables are the gross monthly wage (salary), hourly earnings and worked and non-worked hours. Definitions of these variables are specified below.

Gross monthly wage applies to the whole time period taken into consideration. Unlike the hourly earnings, gross monthly wage is calculated on the basis of other directly surveyed wage items and non-wage fulfilments. It is a summary of these wage items: wage, wage compensations and remuneration for work readiness. The resulting sum is divided by the number of employee's adjusted paid months, i.e. the number of months corresponding to the sum of worked hours and hours, for which the employee was paid the wage compensation. If the employee was included in the registered numbers for a period shorter than the monitored one, his number of paid months will be reduced by the proportion of the number of work days in the registered numbers to the one in the monitored period. The number of paid months will be reduced similarly if the employee had an absence other than an absence with wage compensation or had a shorter workload agreed. Only those employees are included in the calculation of the gross monthly wage who worked for the concerned employer at least for one month and at the same time their set weekly working hours amounted to at least 30 (as recommended by Eurostat).

Hourly earnings are a directly surveyed item. Only those employees are included in the calculation who were in the registered numbers as of the last date of the monitored period.

Monthly worked hours also apply to the whole monitored period and are calculated as a ratio of the employee's monthly worked hours for the monitored period and the number of the employee's adjusted registered months which correspond to the length of the workload and employment in the monitored period. If the employee was included in the registered numbers for a period shorter than the monitored one or had a shorter workload agreed, the number of registered months shall be proportionally reduced. Monthly non-worked hours are calculated in a similar way as worked hours and the average monthly data about overtime work, holiday leave and illness.

As for the publications for the first half year and for the whole year, the time period corresponds to the period from the beginning of the year until the end of the quarter for which the statistical survey is carried out (i.e. Q1 - Q2 and Q1 - Q4 of the relevant year). As for the publications for individual quarters, the monitored period is always the specific quarter for which the statistical survey is carried out (i.e. Q1, Q2, Q3 or Q4).

You can find a detailed description of all the above mentioned variables in all ISPV publications in PDF format and in the Calculation Algorithms for ISPV and RSCP. Descriptions of items of the record on the economic subject (MI file) and on employment (MP file) are specified in the Handbook of Preparation of Input Data for the ISPV.

Statistical Characteristics

Statistical characteristics specified in the results are a median and an average. The results are also differentiated by the first and third quartile and the first and ninth decile.

The median is the value which divides an arranged line of numbers into two equal halves. It applies that at least 50 % of values are lower than or equal to the median and at least 50 % of values are higher than or equal to the median. The basic advantage of the median as a statistical characteristic is the fact that unlike the average it is not affected by any extreme value.

Quartiles are values dividing a line of numbers in an ascending order into quarters. The first quartile is the value below which there are 25 % of the lowest values from the arranged line. The third quartile is the value above which there are 25 % of the highest values from the arranged line. The second quartile is equal to the median.

Deciles are values dividing a line of numbers in an ascending order into ten parts. The first decile is the value below which there are 10 % of the lowest values from the arranged line. The ninth decile is the value above which there are 10 % of the highest values from the arranged line.

You can find a description of the above mentioned statistical characteristics also in all ISPV publications in PDF format.

Main Changes in the ISPV Survey Since 2011

In 2011, several changes were made in ISPV. The main changes are as follows:

  1. A change of terms. Since 2011, ISPV has been using the term wage sphere instead of the business sphere and the term salary sphere instead of the non-business sphere.
  2. Changes in publications. As of 2011, the periodicity and contents of individual ISPV publications changed. A publication about wages and working hours classified according to the sector of economic activity is issued for each quarter. For each even quarter, this publication is extended by information about hourly earnings. Publications for the wage and salary spheres including data about wages and working hours in detailed classifications, in particular according to the individual occupations, are issued for the first half year and for the whole year. Once a year, publications for individual regions of the Czech Republic are issued within the Regional Earnings Statistics (RSCP).
  3. A harmonization of the ISPV methodology with the Czech Statistical Office (CZSO). Since 2011, the methodology for data processing included in ISPV is harmonized with the wage statistics of the CZSO. The benefit of the harmonization rests in improved quality of both of the published wage statistics.
  4. An estimate quality of gross monthly wage median. In the half-year publication for the wage sphere, the quality of the gross monthly wage median was published for the first time.
  5. Occupations according to the classification CZ-ISCO. In 2011, there were significant changes made as far as classification of occupations is concerned. The original classification KZAM-R was changed for the new classification CZ-ISCO. Due to the change of the classification, results according to the occupation specified in the half-year publications for 2011 for the wage (or salary as the case may be) sphere in the tables MZS-M7 and MZS-M8 (or PLS-M7 and PLS M8 as the case may be) cannot be subject of the year-to-year comparison with the results specified in the tables for the business (or non-business as the case may be) sphere until 2010 (tables PS-M1 and PS-M5, or NS-M1 and NS-M5 as the case may be).

Detailed description of changes you can find here, or in individual ISPV publications for 2011.

Harmonization of the ISPV Survey with the Wage Statistics of CZSO

MIn 2011, the ISPV methodology was harmonized with the methodology applied within the wage statistics of the Czech Statistical Office (CZSO). Within the harmonization, the ISPV population was extended by economic subjects not monitored before.

The ISPV population was extended by the employees of:

  • legal persons with less than 10 employees,
  • natural persons and non-profit institutions regardless of the number of employees.

The benefit of the harmonization rests in improved quality of the published wage statistics. The extension of the ISPV population allowed to calculate more accurate numbers above all on employees and thus since 2011, all ISPV publications has newly stated weighed numbers of employees.

Due to the above mentioned harmonization, the gross monthly wage median for the wage sphere decreased in 2011. In order to be able to carry out a correct comparison of the wage development, the publications include year-to-year indices calculated using the revised data for 2010..

Main Differences between the Wage Statistics of the CZSO and the ISPV

In 2011, the ISPV methodology was harmonized with the methodology applied within the wage statistics of the Czech Statistical Office (CZSO). Nevertheless there are still differences between both surveys due to the specifics of the ISPV survey. Detailed information about the harmonization is specified above or here; differences between ISPV and the wage statistics of the CZSO are described here.

The ISPV Quality Reports

The Average Earnings Information System (ISPV) is the only source of structural wage statistics in the Czech Republic and therefore also the main source of data for the Structure of Earnings Survey (SES). The SES is carried out in individual countries of the European Union in a four-year cycle. For this reason, on the basis of the Commission Regulation (EC) No. 698/2006, reports on quality of ISPV survey for the wage sphere (until 2010 called the business sphere) are issued regularly. Quality of the statistical data about wages as well as the quality of the survey process is assessed according to the criteria important for the user, processor as well as administrator of the statistical survey. Criteria for assessment of ISPV quality are relevance, accuracy, punctuality and timeliness, accessibility and clarity, comparability and cohesion. Individual aspects are described in detail in the Report on Quality of ISPV - PS for 2009.