August closed the month up 3.36% from the July close. Let's review how the month has behaved in the S&P 500 since 1928.

Each bar in the chart shows the August close change from the July close. Historically, August has been a good month, with an average gain of 0.88%. August 2009 ranks 21st in this 82-year timeframe (down from 14th place as of yesterday's close).

For previous posts on seasonality, see my "Behavior of the Months" series: Part 1, Part 2 and Part 3. For an interesting international website with more detail on seasonality and the driving forces behind it, see seasonalcharts.com.

September has a very different history, which we'll examine tomorrow.