Confidence among U.S. consumers plunged in August to the lowest level since May 1980, adding to concern that weak employment gains and volatility in the stock market will prompt households to retrench.

The Thomson Reuters/University of Michigan preliminary index of consumer sentiment slumped to 54.9 from 63.7 the prior month. The gauge was projected to decline to 62, according to the median forecast in a Bloomberg News survey.

The biggest one-week slump in stocks since 2008 and the threat of default on the nation’s debt may have exacerbated consumers’ concerns as unemployment hovers above 9 percent and companies are hesitant to hire. Rising pessimism poses a risk household spending will cool further, hindering a recovery that Federal Reserve policy makers said this week was already advancing ‘considerably slower