Over your six month time period stocks like Dow Chem, Monsanto, Dupont, Potash and even most of the Agribusiness ETF's ( Moo, Fud and Jja)have all experienced similar percentage gains (+45% to +55%). Monsanto is a tad higher than the group (around 5%) which I would say is because of its recent reporting.
The Sector as a group has been put in favor. Can we call it market inefficiency?
I guess the real question is which period is efficient.