During the 1973–1974 stock-market crash, the S&P 500 lost about 48% from peak to trough.
The decline began after the S&P 500 reached a closing high in January 1973 and continued until October 1974. The index fell amid inflation, recession, political uncertainty and the effects of the 1973 oil crisis. The collapse was one of the most severe U.S. bear markets since the Great Depression.
The 1973 oil embargo, imposed by Arab members of OPEC against several countries including the United States, caused energy prices to surge. At the same time, the United States faced economic stagnation combined with inflation, a condition later called stagflation. These pressures damaged corporate profits and investor confidence.
The S&P 500 eventually reached its bear-market low on October 3, 1974. The exact percentage can vary slightly depending on whether a source uses closing or intraday prices, but roughly 48% is the standard figure for the peak-to-trough decline.