A survey showing the services sector of the economy is faring no better than the nation's factories was contributing to the weakness in stocks Thursday.

The Institute of Supply Management's index for services, by far the largest part of the economy, came in at 50.9 in August. While anything over 50 indicates expansion the August reading showed the slowest pace since January, and was down from 53.1 in July.

The reading measures activity among financial services, construction, retail and other non-manufacturing businesses. Economists had been a reading of about 54 in August.

The disappointing number exacerbated losses in the Dow Jones Industrial Average, which was trading down about 100 points at noon.

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On Tuesday, the ISM's U.S. factory index came in at a disappointing 50.5 in August, unchanged from July and slightly below economists' expectations.

Thursday's services report showed that new orders for service companies fell to 51.6 in August from 52.6 in July. Order backlogs rose to 48 from 43.5.

The report is based on a survey of 375 companies in 17 industries. Ten industries reported growth in August, led by entertainment, utilities and real estate, according to the report.