Economists had predicted the private sector would pick up 180,000 jobs in the month. In addition, ADP dropped its August estimate of new jobs from 176,000 to 159,000.
In September, ADP said firms with under 50 employees added 74,000 jobs in the month, while companies with at least 500 on the payroll added 64,000. Mid-sized firms gained 28,000 jobs in the month, ADP said.
With the government partially shut down, the monthly report may have more impact than it normally does.
Each month, the ADP report is overshadowed by the Labor Department's Employment Situation report, which is scheduled for release on the Friday after the ADP report. With no budget agreement in sight, however, the ADP report may be the only major monthly employment measure released.
The ADP report lacks data on public sector jobs that the Labor Department monitors.
ADP noted that September's gains were largely in the service sector, which gained 147,000 jobs compared with goods-producing companies that added 19,000.
Construction companies added 16,000 jobs in the month, while manufacturing firms added 1,000. Companies listed under trade, transportation and utilities added 54,000 jobs, while financial firms lost 4,000 positions in September.
Professional and business services jobs rose by 27,000 in the month, ADP said.
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