Stocks dropped sharply in late afternoon trading but still managed to end May higher. The Dow average ended the day with its biggest loss in nearly six weeks. Some traders said the sudden swoon was due to investors rebalancing their holdings at the end of the month. As stocks fell, bonds rallied. Markets started the day slightly lower after the government reported that Americans cut back on spending in April. That was offset by a University of Michigan report showing that a measure of US consumer confidence jumped to the highest level in almost six years in May, lifted by rising home prices and record-high stock prices.