Monster’s employment index of online job posting activity in the U.S. fell to a reading of 153 in September, down three points from August’s reading, Monster Worldwide Inc. reported. The index is still up five points from its September 2011 reading.

Fourteen of the 20 industries monitored for the index showed annual growth. Top industries include retail trade, up 12 percent; construction, up 11 percent; transportation and warehousing, up 11 percent; administrative, support and waste management services, up 10 percent; and agriculture, forestry, fishing and hunting, up 8 percent.

The index is based on a review of online job ads taken from a selection of websites, including Monster.com.