Economic activity in the Midwest contracted at the fastest pace in more than six years in December, according to the Chicago Business Barometer, also known as the Chicago PMI.

The index fell to 42.9 from 48.7 in November. Economists had expected it to rise 1.3 points to 50 in the December reading. The index has spent much of the year below the 50 mark that separates expansion from contraction.