Backtesting of S&P 500 historical data from 1950 to November 6, 2026, reveals that buying after the index closes at a record high yields an average 9.80% return over the next 12 months, with a 75% probability of increase. This is essentially the same as the 9.42% average return and 75% probability of increase for buying on any trading day. If repeating days of consecutive record highs are excluded, and only the first trading day of each record high is retained, the average return over the next 12 months remains 8.30%; since 1990, this figure has further increased to 11.99%, with an 84% probability of increase. However, short-term performance is relatively weak, with an average increase of only 0.28% in the 21 trading days following a record high, lower than the 0.76% increase on a normal trading day. The range of returns for a single 12-month period ranges from a 37.1% decline to a 44.2% increase, indicating that a good historical average performance does not guarantee the absence of significant drawdown risk. Research shows that a record high itself is not a reliable warning signal of a long-term market decline. This data is from Backtested and is for reference only, not investment advice.
