Which market model appears to dry weather unexpectedly cut the 2003 soybean harvest by 15 percent, making it the smallest harvest in seven years. China increased its demand for soybeans, acquiring a record 300 million U.S. bushels between September 2003 and April 2004. The Bush administration expected that U.S. farmers would respond to the high prices by planning more soybeans in the next cycle. Please explain the behaviour described.