Miss the market’s 10 best days over a couple of decades and your long-run return can be cut roughly in half — and those best days often cluster right next to the worst ones.

Since 1928 the S&P 500 has finished the year higher about 73% of the time — roughly three years in four end in the green. Down years are impossible to predict in advance, but the base rate quietly favors staying invested.

Over the long run the S&P 500 has returned roughly 10% a year on average before inflation — but almost no individual year actually lands near 10%. The average hides wild swings.