Percent, points and the log scale

Two charts, the same prices

Both charts show the S&P 500 at the end of each month since January 1928, when the index stood at 17.57 points. On Nov 6, 2026 it closed at 7,377, about 420 times as high. The index leaves out dividends.

On the ordinary chart everything before the 1990s looks like a flat line. The fall of 1929–1932 was 86%, but only 27 points, so it barely shows. The fall of 2022 was 25% and 1,220 points, and looks far bigger although it was smaller in percent.

On the logarithmic chart the distance from 10 to 100 is the same as from 100 to 1,000. There 1929–1932 shows as the deep fall it was.

Points and percent

How many points the index moves depends on where it stands. From 17.57 it took 40 years to reach 100; the first month to end above 100 was September 1968. From there it took 30 years to reach 1,000, in February 1998. The first step was +469% and the second +900%. In points the second step was 11 times the first; in percent it was not even twice as large.

The largest one-day falls, in points and in percent:

The largest fall in points, 335 points on Nov 5, 2026, was 4.4%. The largest in percent, 20.5% on Oct 19, 1987, was only 58 points. A headline that the market fell a number of points says little without the percentage.

When to use which

For a few months it hardly matters, because the price cannot change enough for the scale to show. Over many years, and especially once a price has multiplied, the log scale shows best how an owner did. Compare percentages, not dollars or points. How much the market has gained per year is in the average return study, and every crash since 1928 in the crash study.