I wonder why SF-12 variables are available twice in Waves 2 to 5: as usual variables and as self-completion. For instance, b_sf1 and b_scsf1 represent the same question on general health. What is most confusing: there are a lot of participants who have valid answers on both variables, and a simple crosstabulation of these variables shows that the answers are not identical for many participants. That is, one and the same person may have reported that their health is excellent (according to b_sf1) and fair (according to b_scsf1). I would be happy to find out which of these (groups of) variables is the "real" record of participants' responses to SF-12.