American manufacturers said orders from customers slowed sharply in January after hitting a more than four-year high in December. Unusually cold and snowy weather last month was said to be largely the blame for the decline.

The Institute for Supply Management index sank to 51.3% from 56.5% in December, marking the lowest level in eight months. The decline was much greater than Wall Street expected, i.e., economists polled by MarketWatch only expected the index to slip to 56%.

The report noted that the biggest one-month reversal in the new-orders index since December 1980 was the main culprit. The new-orders index plunged 13.2 points to 51.2%, also the lowest reading since May.

The ISM index tends to rise or fall in tandem with the health of the economy. Eleven of the 18 U.S. manufacturing industries surveyed by ISM reported growth in January.

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