My 'Bait & Switch' light turned on half way through:

The author tries to move between mech-eng analysis (under controlled experimental conditions) - "what happens to this piece of metal in a 25 mph crash? how about 30?" vs. social-science analysis - "what happens to crashes when the state changes the excise tax on alcohol?"

It's not like there could be any confounding variables between states Oregon vs. Kentucky, the 1970's vs. the 1990's etc. It's all just data and engineers, right?