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What does the microcensus describe?

The microcensus provides official representative statistics of the population and the labour market in Germany. The Labour Force Survey of the European Union (EU Labour Force Survey) forms an integral part of the microcensus. Since 1957 - in the new Länder (including Berlin-East) since 1991 - the microcensus has supplied statistical information in a detailed subject-related and regional breakdown on the population structure, the economic and social situation of the population, families, consensual unions and households, on employment, job search, education/training and continuing education/training, the housing situation and health.

The purpose of the microcensus is to provide benchmark and structural data at regular and short intervals on the above-mentioned topics and their development, thereby bridging the data gap between two population censuses. The microcensus is designed as a multi-topic survey, integrating many different subject fields. With regard to a number of small-scale surveys of empirical social and opinion research as well as of official statistics, the microcensus is a tool for extrapolation, adjustment and control. In addition, what is a major tool for European and national users is the Labour Force Survey which is integrated into the microcensus and is harmonised in all EU member states, thus allowing comparisons to be drawn on issues of labour force participation and unemployment. The majority of the variables covered by the Labour Force Survey are also microcensus variables.

The results of the microcensus are used in government reports and in the annual report of the German Council of Economic Experts; they provide the basis for current employment research, for the Federal Government's annual Pension Insurance Report and much more besides. The results of the Labour Force Survey are used, for example, to calculate the EU indicators on employment policy and sustainable development and to distribute money from the regional and social funds of the European Union. Also, the Labour Force Survey is the basis for monthly reporting on unemployment in the EU member states.

How is the microcensus conducted?

The microcensus is organised as a decentralised statistics, which means that the organisational and technical preparation is done at the Federal Statistical Office, while conducting the survey and processing the data are tasks of the statistical offices of the Länder. It is based on a law with a limited period of validity, the Microcensus Law. In 2004, the former "Law on the Execution of a Sample Survey of the Population and the Labour Market and of the Housing Situation of Households" of 17 January 1996 (Microcensus Law 1996; Federal Law Gazette I, p. 34) was replaced by the same-named Microcensus Law of 24 June 2004 (Microcensus Law 2005; Federal Law Gazette I, p. 1350). The new legal basis for the microcensus has led to content-related and methodological changes in the microcensus design for the years 2005 to 2012.

Until 2004, the survey design of the microcensus was characterised by a fixed reference week, which means that the majority of questions referred to the situation in a single reference week per year. Usually that was the last holiday-free week in April. Consequently, the microcensus results up to 2004 provided a snap-shot of the conditions in spring and were affected to differing degrees - depending on the variable concerned - by seasonal variations. Section 3 of the Microcensus Law 2005 provides for a continuous survey. In that type of survey, the entire survey volume is to be distributed evenly over all calendar weeks of the year, with the last week preceding the survey being the reference week (so-called moving reference week). The goal is to provide microcensus users not only with annual but also with quarterly average results. The quarterly publication of quarterly results, however, is currently under examination because of methodical problems.

As regards the list of questions included in the microcensus, Section 4 of the Microcensus Law 2005 lays down the topics to be covered in the individual years and their periodicities. In contrast to the law applicable up to 2004, there are no sub-samples any longer, so that there is a general sampling fraction of 1% of the population for all variables. This makes the microcensus the largest annual household survey in Europe. As in the years from 1996 to 2004, the question programme consists of a standard programme of variables that are covered every year, and a number of variables that are covered only at four-year intervals (4-yearly additional programmes, for example questions on health).

The content-related changes in the microcensus survey programme as from 2005 mainly relate to the inclusion of a new set of topics on "migration and integration". One part of the respective questions is covered every year, the other at four-year intervals. The section on "education" for the first time includes questions on the field of highest vocational qualification and on the kind of vocational qualification besides a higher education degree. To avoid increasing the burden on the respondents, some variables have been deleted from the microcensus question programme (for example year of marriage; current attendance of nursery school, crèche or day care centre for school children; usual and actual hours worked per week (in terms of days); need for long-term nursing care; change of local unit).

The microcensus is a random sample in which all households have the same probability of selection. Within the territory of the Federal Republic of Germany, areas (sampling districts) are selected in which all households and persons are interviewed (one-stage cluster sample). Every year, a quarter of the households (or sampling districts) included in the sample are exchanged. This means that each household remains in the sample for four years (partial rotation procedure).

A variety of survey instruments are used in the microcensus. The majority of data are collected by interviewers from the statistical offices of the Länder, who conduct face-to-face interviews with all persons in a household. However, the household members may also complete a paper questionnaire (written survey), which applies to a good 20% of the households covered. There is an obligation to provide information for most of the questions, while only for a small number of variables the law provides for voluntary response. Variables which are exclusively covered for purposes of the EU Labour Force Survey are always subject to voluntary response. Proxy interviews are permissible in the microcensus, which means that one household member may supply information on other household members. Proxy data are collected on about 25% to 30% of all persons aged 15 years or over.

Due to the obligation to provide information, the share of known non-response in households to be covered (unit non-response) is very small at about 5%. The share of non-response for individual questions or variables (item non-response) is generally well below 10%. It may however be considerably higher in individual cases, especially for sensitive variables with voluntary response. Compared with the microcensuses conducted up to 2004, item non-response has decreased. The main reason is probably the fact that, when changing over to the continuous survey, the use of laptops was introduced everywhere, which in turn resulted in a further standardisation of the interviews.

When are the microcensus results published?

Annual results are available about three months after the end of the survey year. Due to methodical effects, the monthly and quarterly trends are characterised by high volatility. For that reason the Federal Statistical Office has published only annual results (annual averages) so far. The issue of publishing quarterly results is currently being examined.

The federal results of the microcensus are published as online products in publications as well as in various Subject-Matter Series and cross-section publications of the Federal Statistical Office. Comments on the results and methodological papers are published, among others, in the journal "Wirtschaft und Statistik" (Economy and Statistics, published monthly by the Federal Statistical Office). Results concerning topical issues are presented at a press conference and in press releases. The release calendar and the press releases can be found on the Federal Statistical Office's website. Apart from federal results, a great variety of data for the Länder are available, which are published by the respective statistical offices of the Länder.

How accurate is the microcensus?

Sample surveys like the microcensus involve two kinds of errors: random sampling errors and systematic errors. Random sampling errors are deviations arising from the fact that not all units of the population are included in the survey. The standard error, which is calculated using the individual data of the sample, serves as an estimate for the random sampling error. The simple relative standard error exceeds 15% for extrapolated annual results of less than 5,000 and - if based on provisional figures - extrapolated quarterly results of less than 20,000, which relate to fewer than 50 persons in the sample. Such results are of little informative value and should therefore not be used for comparisons. This is why extrapolated cell frequencies of less than 5,000 at an annual level or less than 20,000 at a quarterly level are not shown in microcensus publications but are replaced by a slash ("/").

Systematic errors are non-random deviations which may arise from errors occurring at any stage of statistical production (for example deficiencies in adequate questionnaire design and interviewer training, wrong information provided by respondents and interviewers, data capture errors). Although marked improvements have been achieved in the last few years, the results of the microcensus regarding the labour force participation measured according to the labour force concept of the International Labour Organization (ILO concept) still differ in part from the results of other data sources of labour market statistics. For 2008, the number of persons in employment shown by the microcensus is by 3.8% smaller than the figure obtained in employment accounts as part of national accounts.

More detailed comparative analyses indicate that there are differences especially for small-scale and minor activities and for the search for such activities. To examine those differences, a follow-up survey was conducted in 2008 as part of a Federation/Länder project. About 4,000 persons who had participated in the microcensus before were questioned by telephone again on their employment status by the participating statistical offices of the Länder. The survey tool of a follow-up survey was optimised specifically to cover small-scale activities and secondary jobs. Comparisons drawn between the information given in the microcensus and that of the follow-up survey clearly show that, in many cases, especially pupils, students and pensioners with a casual job or minor employment had indicated such activities only in the follow-up survey. It must therefore be assumed that those groups of persons, who in their everyday concepts do not consider themselves as persons in employment, base their answers particularly on their main social status (e. g. pupil or pensioner) and do not always think that the microcensus questions on labour force participation apply to them. The effects of proxy interviews, however, are smaller: About one quarter of the answers are given by other household members on behalf of those to be covered. The follow-up survey showed that the effects of proxy interviews can explain only a small part of the differences in results. Although in some subject fields differences were observed between the information given by other persons in the microcensus interview and the information provided in the follow-up survey by the persons to be covered, most of those differences are within the range of differences observed for all respondents, irrespective of whether the information was provided by themselves or by other persons in the microcensus/LFS.

The undercoverage of marginal employment does not only result in an underestimation of the overall level of employment and hence of the employment/population ratio. What is also affected is the structure of employment, for example the breakdown of persons in employment according to demographic variables such as age and sex, by part-time and full-time employment or the average number of hours worked.

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