Friday, April 17, 2009

Anchoring Vignettes: Sample Selection Issues and Longitudinal Aspects

Omar Paccagnella from the Dept. of Economics at the University of Padua has a working paper on "Anchoring Vignettes with Sample Selection". The paper aims at extending the standard (hopit) model for estimating vignettes in order to allow the specification of some selection variables.

The concern about sample selection arises from when a respondent in the SHARE (ageing) study completes the main CAPI questionnaire, but does not fill in the extra questions that they have been randomly assigned to - which are anchoring vignettes. Paccagnella states that fitting models to the observed sample ignoring potential selection bias may lead to inconsistent estimates. His findings show that there is evidence of sample selection effects even in the case of high rates of collected vignettes (higher than 85%), but in such cases the bias induced by the selection mechanism is negligible.

Paccagnella also has a working paper in presentation format: on using anchoring vignettes in a longitudinal context, examining work disability reporting from SHARE. This work concludes that when moving from one wave of the SHARE study to the other, that individual thresholds shift upwards and that respondents assess a work limitation less easily in 2006 than in 2004. Also, variations over time in work disability reporting are reported to be much stronger than variations across countries.

Paccagnella has also written on using vignettes to enhance the comparability of self-rated life satisfaction, using the SHARE data. And a paper on voluntary private health insurance for the over-50's, also using the SHARE data.

No comments: