The Institute for Supply Management-Chicago Inc. said today its business barometer decreased to 55.9 in March from 59.8 the prior month.

The median forecast of 45 economists in a Bloomberg survey called for the index to be unchanged at 59.8 Readings greater than 50 signal growth.

Projections in the survey ranged from 56 to 62. The national factory index, produced by the Tempe, Arizona-based Institute for Supply Management, probably rose to 54 in March from 53.2 the prior month, according to the median projection in a Bloomberg survey ahead of tomorrow’s release.