Impossible, right? As a money manager I spend a decent amount of time explaining to clients, readers, family, and friends that the stock market does not mirror the economy in real time. Just because the unemployment rate is 9.5% and GDP growth is decelerating does not mean that the stock market is a poor investment option. Stock market returns and GDP growth simply do not track each other, and as a result, reading economic reports will not help you figure out where stock prices are headed.

As always, I try to present numbers to people so they do not simply have to take my word for it. In today's world of media sound bytes and political maneuvering Americans all too often repeat something they heard from one of their favorite media or political pundits as if it was fact, even when a tiny bit of research can disprove the claim.

In order to show that stock market movements do not mimic the economy, I decided to compile data from 1958 (the first full year the S&P 500 index was published) through 2009. While I had no idea what the actual numbers would be, I was confident they would show that stocks and the economy shared a very low correlation. Sure enough, the results were even surprising to me. It turns out that the S&P 500 has performed best when GDP growth is actually negative (i.e. when the economy is in a recession). Since 1958 there have been 7 years when U.S. GDP shrank and the S&P 500 gained an average of 24% per year during those periods. Pretty interesting, right?

Here is the full data set. I divided economic growth into 4 subsets (negative, zero to 3%, 3 to 5%, and above 5%).

As you can see, there is very little correlation between the economy and the stock market. Not only that, investors choosing to own stocks only in years with negative GDP growth would have earned nearly 4 times as much than investors choosing to invest only when GDP was growing at 5% or better. So the next time someone tells you the market is going to drop because the economy is bad or unemployment is high, send them a link to this blog post.