Since 1950, the S&P 500 has seen monthly gains exceeding 10% 14 times. Historical data shows that these surges did not significantly exhaust short-term market potential: the average subsequent three-month gain was 4.7%, higher than the normal 2.2% for the same period, with a probability of 78.6%.
Long-term momentum is even more pronounced. In the 13 samples with complete one-year data, the market continued to rise in 11 of them, a probability of 84.6%; the average 12-month gain was 16.4%, also significantly higher than the 9.3% for the same period in all years. This indicates that extreme monthly gains often occur during trend corrections or the start of a new market cycle, and do not necessarily mean that the upside potential has been prematurely exhausted.
However, the sample only includes 13 instances, and the 1987 surge was followed by a 6.2% decline in the year afterward, while the decline after 1980 was even greater, at 10.1%. Historical statistics provide conditional probabilities and cannot answer whether the current valuation, AI capital expenditure returns, and macroeconomic risks have been fully priced in.
