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The Institute for Supply Management said its US factory index unexpectedly fell to 49.5 in November from 51.7 in October.
A reading below 50 indicates manufacturing is contracting.
Benchmark 10-year Treasuries prices were 6/32 lower with a yield of 1.634 percent.
They were down 8/32 with a 1.642 percent yield prior to the release of the ISM data.