Two of the four broad categories that make up the headline index made gains from November, while two declined, the Fed said.
The categories making a positive contribution were production, which includes income, and employment. The declines came from personal consumption, which includes housing, and sales orders and inventories.
The index, referred to as the Chicago Fed National Activity Index gave up 0.02 in December from 0.27 in the previous month.
The index assigns a base value of zero to the standard upward trend that is normal for businesses. Figures above zero indicate business growth is above normal.
The CFNAI three-month rolling average in December rose from minus 0.13 in November to minus 0.11 in December, posting its 10th consecutive month below zero.
That does not necessarily indicate a contraction, but growth slower than the normal trend. It also "suggests subdued inflationary pressure from economic activity over the coming year," the Fed said.