Rob Inglis doesn't think Obama's proposed reform of the direct payments program will do much to diminish the distortions in the agricultural sector. It eliminates wasteful direct payments to large producers rather than shifting the mix of crop subsidies. It's more like eliminating a tax break for rich farmers than changing the price of corn. Good tax policy, but not necessarily here or there so far as food policy goes. Tom Laskawy has more, as does Jill Richardson. Here's the relevant part of the budget (pdf).
