The University of Michigan's final August consumer sentiment index fell slightly to 87.6, down from 88.1 in July and a mid-month reading of 87.9, market sources said Friday.

With the stock market surging roughly 20 percent in the past month after plunging more than 30 percent between April and late July, most confidence measures have steadied.

The final August current conditions index edged lower to 98.5 from 99.3 in July and a mid-month reading of 100.2, while the expectations index, which tracks attitudes about the 12 months ahead, slipped to 80.6 in August from 81.0 in July but was above the preliminary reading of 80.0.