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Q2008 – European Conference on Quality in Official Statistics Rome • July 9-11, 2008

The Effect of Questionnaire Length on Response Rates and Level of Estimates in the German Job Vacancy Survey Hans Kiesl Institute for Employment Research (IAB), Germany. Q2008 – European Conference on Quality in Official Statistics Rome • July 9-11, 2008. Background.

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Q2008 – European Conference on Quality in Official Statistics Rome • July 9-11, 2008

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  1. The Effect of Questionnaire Length on Response Rates and Level of Estimates in the German Job Vacancy Survey Hans Kiesl Institute for Employment Research (IAB), Germany Q2008 – European Conference on Quality in Official Statistics Rome • July 9-11, 2008

  2. Background • Regulation (EC) No. 453/2008 of the European Parliament and of the Council of 23 April 2008 on quarterly statistics on Community job vacancies • Member states have to provide • quarterly data on job vacancies (broken down to NACE section level) • quality reports In Germany, the data will be provided by the IAB.

  3. Background (2) • 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 NACE-sector) • Since 1989, IAB conducts a yearly (4th quarter) 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); voluntary • CATI interviews in quarters 1 - 3

  4. Basic sampling design • stratified SRS; 16 sectors  7 size classes x West/East • sampling rates and sample sizes in different size classes (IV/2006):

  5. Highly skewed distribution of job vacancies

  6. Highly skewed distribution of job vacancies % of Zeros:

  7. Problem: extremely low response rates

  8. Reasons for non-response • After fall 2007 survey, CATI sub-sample of non-respondents to • find out main reasons for non-response • sample of 1292 business units • 6% no/wrong telephone number or late respondents • 15% not willing to respond • 79% respondents; their reasons for non-response in job vac. survey: • 54%: no time; too much work (72% for largest units) • 20%: no job vacancies (25% for smallest units) • 4%: no relevant topic (44% for smallest units) • 7%: take part in surveys only if mandatory • 7%: never take part in surveys

  9. Impact of length of questionnaire (1) • During the 4th 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; 9,450 sampling units). • Research 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)

  10. Impact of length of questionnaire (2) • Response rates by size of business units:

  11. Response rates by sector: Impact of length of questionnaire (3)

  12. 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 • Linear GREG, using CLAN (Statistics Sweden) • Results quite robust with regard to underlying model e.g. constant variance or variance proportional to (1 + number of registered vacancies) Weighting and estimation

  13. Impact of length of questionnaire on estimated number of job vacancies (1) (Note: differences to officially published results due to slightly different weighting)

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

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

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

  17. 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). • Indication that non-response bias might be only modest.

  18. Thank you very much for your attention! Q2008 – European Conference on Quality in Official Statistics Rome • July 9-11, 2008

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