Common investing advice, tested against real market data. I publish the code, the data, and the cases where the answer flips.https://checkedthemath.com/enhttps://checkedthemath.com/posts/what-perfect-market-timing-is-worth/https://checkedthemath.com/posts/what-perfect-market-timing-is-worth/Buying at every yearly low instead of every yearly high was worth about 27 percentage points. Here is every window since 1928, not the one usually quoted.Wed, 26 Aug 2026 00:00:00 GMThttps://checkedthemath.com/posts/does-buying-the-dip-work/https://checkedthemath.com/posts/does-buying-the-dip-work/Waiting for a pullback sounds obviously smart. Across 225 rolling 20-year windows of S&P 500 data, waiting for a 5% or 10% dip won exactly zero times.Tue, 25 Aug 2026 00:00:00 GMT