[Someone]

AFAIK, in the EU, the UK is the only country that has single-payer healthcare (http://en.m.wikipedia.org/wiki/Single-payer_health_care#Sing...), so I doubt that is the deciding factor.

My money would be on a) more people having insurance, b) having resident registration (that database will have errors, but in cohort studies, people spend lots of time trying to correct that for those in a cohort), c) people, in general, to have more trust in government, certainly where it concerns healthcare, and d) government more willing to look ahead further. I do not have supporting data for c) and d)