David Leonhardt writes today about the battle over a tax on soft drinks. I've written before about taxing junk food. I've also written about the awful incentives our back-asswards subsidies give. A tax on junk food, especially soft drinks, is good policy. Anytime you can raise revenue while providing disincentive to risky or bad behavior, it's a win. But even if you don't read the article, look at the chart he posted. Over the past 30 years, the only foods whose prices have risen are fruits and vegetables and, to a much lesser extent, breakfast cereal. Soft drinks have dropped in price the most. If we can make it cheaper and easier for people to eat healthier and more expensive and difficult to eat crap, we can make headway against obesity in this country.