Using Register Data to Evaluate the Effects of Proxy Interviews in the Norwegian Labour Force Survey
Ib Thomsen, Ole Villund
We combine data from the Norwegian Labour Force Survey with register data in order to evaluate the impact of proxy interviews on the survey-based employment rate estimates. The method compares estimates under different models for proxy response and nonresponse models, over a relatively long time series from 1997 to 2008. Using register-based employment as an auxiliary variable, we try to differentiate between the effect of the measurement and the effect of the fact that proxy-interviewed people are not selected at random. We label these effects proxy effect and selection effect respectively, and suggest methods for estimating them. Our conclusion, after also including the impact of nonresponse, is that proxy interviews probably result in a better employment rate estimate, even though they introduce some underreporting. The reason is that proxy interviews provide data on some hard-to-reach people who have a labour-market situation more similar to that of those not reached at all. We find that including the proxy responses has approximately the same effect as post-stratification of the direct responses, using register-employment status as the auxiliary variable.
Nonresponse, proxy response, nonsampling error, selection bias