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Re-designing the German job vacancy survey assessing the impact of high non-response rates Hans Kiesl, Susanne Rässler Institute for Employment Research.

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Presentation on theme: "Re-designing the German job vacancy survey assessing the impact of high non-response rates Hans Kiesl, Susanne Rässler Institute for Employment Research."— Presentation transcript:

1 Re-designing the German job vacancy survey assessing the impact of high non-response rates Hans Kiesl, Susanne Rässler Institute for Employment Research (IAB), Germany International Conference on Establishment Surveys III Montreal June 18-21, 2007

2 2 Background Information on job vacancies in Germany Business units might report job vacancies to the Federal Employment Agency Federal Employment Agency publishes monthly statistics on number of registered job vacancies (by industry class and NACE-sector) IAB conducts a yearly (4 th quarter) mail sample survey among business units to estimate number of job vacancies (registered or not) and to get additional information (e.g. about recruiting strategies) Mail questionnaire (8 pages in length) In the future: quarterly survey (CATI interviews in quarters 1-3)

3 3 Basic sampling design stratified SRS; 16 sectors 7 size classes West/East sampling rates and sample sizes in different size classes: WestEast ratesample sizeratesample size < 100.9%110673.3%10963 10 - 195.9%853326.1%9546 20 - 497.3%674533.6%8282 50 - 1998.6%454113.3%1815 200 - 49932.9%324950.3%1111 500 - 99968.3%180673.0%395 >= 100075.1%98484.8%193 total2.4%369258.0%32305

4 4 Problem: extremely low response rates

5 5 Reasons for non-response After 2004 survey, CATI subsample of non-respondents to find out main reasons for non-response sample of 1700 business units 26% no/wrong telephone number 16% not willing to respond 58% respondents; their reasons for non-response in job vac. survey: 75%: no time; too much work (88% for largest units) 27%: no job vacancies (41% for smallest units) 25%: no relevant topic (44% for smallest units) 17%: take part in surveys only if mandatory 9%: never take part in surveys

6 6 Impact of length of questionnaire (1) During the 4 th quarter of 2006 (at the same time of the regular survey with 8 pages) a separate survey was conducted (1 page, basic infos, e.g. number of job vacancies). Questions: Has length of questionnaire significant impact on response rates? (Prediction: yes) If so, do different response rates lead to different estimates of number of job vacancies? (Prediction: yes)

7 7 Impact of length of questionnaire (2) Response rates by size of business units: 8 pages1 pageabs. diff.rel. diff. < 1021.0%27.3% + 6.3%+ 29.9% 10 - 1917.0%30.7%+ 13.7%+ 80.1% 20 - 4918.9%28.2% + 9.3%+ 49.1% 50 - 19923.2%28.6% + 5.4%+ 23.2% 200 - 49918.1%27.1% + 9.0%+ 49.9% 500 - 99918.4%28.5%+ 10.1%+ 54.9% >= 100026.8%

8 8 Impact of length of questionnaire (3) Response rates by sector: 8 pages1 pageabs. diff.rel. diff. Agriculture, farming, forestry, fishing24.8%36.5%+ 11.6%+ 46.9% Manufacturing19.6%29.8%+ 10.2%+ 52.3% Construction21.5%28.8%+ 7.3%+ 34.1% Sale, trade, hotels and restaurants, transport, communications14.9%23.3%+ 8.4%+ 56.1% Financial intermediation, insurance, renting and business activities17.3%24.9%+ 7.6%+ 44.0% Public administration, education, health, social work, other service activities23.0%

9 9 Weighting and estimation Calibrate Horvitz-Thompson-estimator to totals from auxiliary data: sampling frame out of date (> 1 year) up-to-date estimates on number of units by size and by sector (no cross-classification) up-to-date estimates on number of employees by size and sector (no cross-classification) registered number of job vacancies by sector Previously: iterative proportional fitting with additional restriction two different weighting factors within each stratum (units with and without job vacancies) no variance estimation Now: linear GREG

10 10 Effect on distribution of weighting factors

11 11 Impact of length of questionnaire on estimated number of job vacancies (1) 8 pagesStandard errorCV 1 page West775,00029,0003.7% 848,00051,0006.0% East212,00010,0004.7% 229,00032,00014.0% Germany987,00031,0003.1% 1,077,00060,0005.6%

12 12 Impact of length of questionnaire on estimated number of job vacancies (2)

13 13 Impact of length of questionnaire on estimated number of job vacancies (3)

14 14 Conclusions Length of questionnaire has considerable effect on response rates (as expected). Change in response rates seem to have only little effect on main survey estimates (job vacancies) (not as expected). Nevertheless split questionnaire design will be adopted in future. Small-scale non-respondent CATI follow-up survey will be conducted every year.

15 Thank you very much for listening! International Conference on Establishment Surveys III Montreal June 18-21, 2007


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