Manufacturing in the U.S. unexpectedly contracted in November as orders dropped to a three-month low and exports slowed.

The Institute for Supply Management's factory index decreased to 49.5, the lowest since July 2009, from 51.7 a month earlier, the Tempe, Arizona-based group said today. Economists projected the index would ease to 51.4, according to the median forecast in a Bloomberg survey. A reading of 50 marks the dividing line between expansion and contraction.

Less corporate investment in equipment as U.S. lawmakers debate the nation's budget, weaker orders from overseas and disturbances related to superstorm Sandy are converging to slow manufacturing. Eleven of the 18 industries covered in the report reported business shrank last month.