Chicago futures reacted today to a record spread between the value of the dollar and the Brazilian real, each at three-year highs and lows, respectively. The response was rational since currency valuations strongly influence the competitiveness of bulk commodities and the U.S. and Brazil produce many of the same agricultural products.  The graph shows the dollar/agricultural export relationship on an annualized basis. Currency valuations are in constant flux as are the supply/demand balances for each supplying country. Consequently, the current situation is not necessarily determinative of the rest of the year. Under normal circumstances, a major purchasing country like China would be heavily influenced by currency valuations but it a...