In a post about how reducing your meat consumption can help you manage food costs, Megan McArdle has the best quote I’ve seen thus far about the food chain:
Also, you may have noticed that meat is getting kind of pricey. Best bet is that it will go up before it goes down, since meat is essentially grain cubed, with a time lag.
UPDATE: As you can see from the comments, a better model is
Meat(t1) = (grain(t0))^3 + [grassfed_dummy(t0)) * (grass(t0) – (grain(t0))^3] + water(t0)