A report from the University of Michigan revealed on Friday the preliminary reading for the Reuters/Michigan index of consumer sentiment surged to 99.2 in early December. That was the highest reading since May.

Economists had expected the index would increase to 97.0 this month from November’s final reading of 96.8.

According to the report, the index of current U.S. economic conditions increased to 115.2 in December from 111.6 in the previous month. Meanwhile, the index of consumer expectations grew to 88.9 this month from 87.3 in November.

Nearly all of the early December gain was among upper-income households, who also reported near-record gains in household wealth, largely due to increased stock prices, the report noted.