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Not sure what you mean, general life choices and what we feel is 'knowledge' is based on such statistics ie don't smoke, wear your safety belt etc. These types of population studies can and should influence politics towards (in this case) a less car-oriented infrastructure for instance.

I should have said (and meant) in respect of cycling. I don't know how it works with these other areas, although I don't think that seat belts are a good example given that there is legislation enforcing their use. There, progress went evidence->policy->law, which is really how it should go, providing the evidence is any good (and the evidence in favour of seat belts has been criticised very strongly by John Adams at least). However, you can't force people to cycle by law, so that progression doesn't work. It's left to individual choice and the extent to which individuals are capable of making decisions on the basis of complex/abstract evidence in the face of other, more powerful influences. I've read dozens of studies on the health benefits of cycling, I know plenty of people who work in the field of public health, etc., and in my experience the actual impact of this (important) work on cycling is negligible. I have various views on why that is, but they take a while to explain.