New York (CNN Business) The manufacturing sector has become the problem child of the US economy.

American manufacturing activity is slowing as rising tariffs have made materials more expensive. The sector shrunk for the first time since September 2009, according to IHS Markit.

Markit's flash manufacturing purchasing managers' index for August fell just below 50, indicating a contraction. It was a 119-month low for the index. A number below 50 means a sector is contracting, while a number above 50 denotes growth.

The August decline comes on the back of weak new orders, which offset slightly faster output, according to Markit. Manufacturing output rose to a two-month high of 50.6.

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