Anchors Down (I) 

 "How's it going?" If you ever tried to compare the answer to this question between the average American ("great") and European ("so-so" followed a list of minor complaints), you hit directly on a big problem in measuring  self-reported variables. 

 Essentially the responses to questions on self-reported health, political voice and so on are determined not only by differences in actual experience, but also by differences in expectations and norms. For a European "so-so" is a rather acceptable status of wellbeing whereas for Americans it might generate serious worries. Similarly people's expectations about health may change with age and responses can thus be incomparable within a population (see this  hilarious video  on Gary King's website for an example). 

 A way to address this problem in surveys is to use "anchoring vignettes"  that let people compare themselves on some scale, and then also ask them to assess hypothetical people on the same scale. The idea is that ratings of the hypothetical persons reflect the respondents' norms and expectations similarly to the rating of their own situation. Since the hypothetical scenarios are fixed across the respondents any difference in response for the vignettes is due to the interpersonal incomparability. 

 Using vignettes is better than asking people to rank themselves on a scale from "best" to "worst" health because it makes the context explicit and puts it in control of the experimenter. Gary and colleagues have done work on this issue which shows that using vignettes can lead to very different results than self-reports (check out their  site ). I will write more on this in the next entry.