The Chicago Purchasing Managers' Business Barometer fell to 49.7 in September from 53.0
The data is compiled on a seasonally adjusted basis. An index reading below 50 signals a slowing economy, while a level above 50 suggests expansion.
Economists polled by Thomson Reuters predicted a 53.0 reading for the indicator.
The production index dipped to 55.4 from 57.4, the new orders index decreased to 47.4 from 54.8, the order backlogs dropped to 41.6 from 41.7 in the prior survey and inventories fell to 51.1 from 51.2. The employment index dropped to 52.0 from 57.1; and the supplier deliveries index was at 52.1, up from 49.9 last month. The prices paid index rose to 63.2 from 57.0.
