Support #1700

Interview timing

Added by Nils Braakmann 3 months ago. Updated 3 months ago.

Survey design
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Dear Understanding Society team,

I was hoping you might be able to help me with a question: We are currently studying the effect of local economic shocks on various individual outcomes. We use the exact timing of the interviews to distinguish between individuals interviewed before and after the shocks. Previous papers (e.g., Powdthavee, N., Plagnol, A.C., Fritjers, P. and Clark, A.E. (2019). Who got the Brexit blues? The effect of Brexit on subjective wellbeing in the UK. Economica 86: 471-494. or Braakmann, N. (2021). Immigration status uncertainty and mental health – Evidence from Brexit. Industrial Relations: A Journal of Economy and Society 60: 521- 548.) have relied on the argument that the timing of the interview is essentially orthogonal to the respective shock (Brexit in the two cases above). I am now currently dealing with a reviewer who has pointed out that "In Germany, there are for instance studies that show that timing of interview correlates with the socio-economic background of the respondents.” This strikes me as a valid point - if there is selectivity on such characteristics and if these characteristics correlate with whatever shock is being looked at, this could indeed cause bias. Before I go and do 20 tests on interview timings and various respondent characteristics, I was wondering whether you have any information about any selectivity or how interviews are timed that you might be willing to share.

All best and thank you in advance,


Updated by Understanding Society User Support Team 3 months ago

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We don't think this is a serious issue for our survey due to way the interviews are conducted. Sample household were are randomly assigned to monthly samples and attempts are made to interview them in those months. There is some variation in actual interview dates because attempts are made to interview non-contacts for a few weeks after which they are coded as non-interviews. If by timing you mean the time of the day or the day of the week - then there may be variation by respondent characteristics as they will choose when to participate.

However, there is some issue of interview date and socio-demographic characteristics once we started web interviews and respondents could choose to respond via web or f2f. Even in those cases, overall the effect is likely to be small. The User Guide has some information about the fieldwork period:
Each month a sample is issued and cases are invited to complete online first (around 70% in the couple of waves pre-pandemic, 100% during the pandemic). After 5 weeks, the remaining households plus non-responding adults who had been invited to complete online are issued to interviewers for face-to-face (or telephone during lockdown). So, if we think that there is some socio-demographic effect on the propensity to complete online, then we will have more of the sample with those web-friendly characteristics taking part in the first five weeks, with a lower proportion of these individuals interviewed in the rest of the fieldwork period. However, one month after that sample were issued, another sample is issued with possibly the same effects. The end result of this, because of continuous fieldwork is at any point in time, we will have a balance of web-friendly/less web-friendly sample members being interviewed. For example, when looking at a particular calendar month, if elderly households are less likely to complete online then they won’t appear at the start of that sample month, but those who were issued a couple of months earlier will appear in the data for that calendar month because they will have taken part in-person or by telephone.

At Wave 7, when web interviews were first introduced, the 23-week fieldwork period for the web-first households was broken up into two weeks of ‘web-only’ fieldwork, 17 weeks of CAPI fieldwork (with the web still available), then four weeks of the telephone mop-up. Adults in households that had responded at Wave 6 were issued directly to interviewers, with a 19-week CAPI fieldwork period followed by a 4-week telephone mop-up. From Wave 8, the web-only fieldwork period was extended to five weeks. During the re-issue phase for these households, non-responding adults were sent a re-issue letter which included information on how to complete their interview online (week 15 onwards).

Hope this helps.

Best wishes,
Understanding Society User Support Team

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