The real reason for our farm policy...

Full employment for economists.

Tyler Cowen counts econo-noses in the federal government.

1. Department of Labor, 1262 economists, 30.5 percent of the total, 1208 of those are at the Bureau of Labor Statistics.
2. Agriculture, 533 economists
3. Treasury, 473
4. Commerce, 462
5. Defense, 225
6. Energy, 168
7. EPA, 163 (is that enough?)
8. HHS, 137
9. Transportation, 88
10. Interior, 86
11. FTC, 74
12. HUD, 62
13. Justice, 61
14. FDIC, 61 (do bank examiners produce the real value there?)
15. All others, 275.  The total is 4130 economists in the Federal government, as of 2008, and I believe those numbers are not counting consultants.
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I was surprised by the comparatively large contingent in the USDA - more than the Treasury or Commerce, for crying out loud!  Partly I think agriculture is ideal for economists to study with thousands of producers or commodities and mountains of relatively good data.

But it doesn't seem to result in good policy, just more of it.