There is a well-known trading strategy that goes by the name of "Sell In May And Go Away". The strategy involves liquidating all of your stock holdings in May and then re-establishing your stock positions in November.  The basic premise of this strategy is when you reference performance data from the stock market for the past 100 years, two of the three worse months typically occur between May and October.  But does it really work?

Losing Strategy

While there are years that we can point to that the "Sell In May" strategy would have worked, it would have been a losing strategy for the past 4 out of 5 years.

The only year that strategy would have worked within the last five years was in 2015 and you avoid a minuscule 1% loss. On the flip side, you missed a huge 11.6% gain in 2017. If you implemented this strategy every year for the past 5 years, it would have cost you 22.4% in investment returns. Not good.

Looking Back Further

Instead of looking back just 5 years, let’s look back 10 years from 2008 to 2017. The “Sell In May” strategy would have only worked 4 out of 10 times. So it would have been the losing strategy 60% of the time. Again, not good.

So why do you hear so much about it? Looking at the market data, even though it has not been a reliable source as to whether or not the stock market will be up or down during the May to October months, the return data of the Dow Jones Industrial Average suggests historically that the largest returns are found during the November through April months.

A perfect example is 2010. In 2010, the Dow Jones Industrial Average produced a return of 1% between May – October. However, the Dow Jones produced a 15.2% rate of return in 2010 between November and April. Implementing the “Sell In May” strategy would have cost you 1% in return since you were not invested during the summer months but you still captured the lion share of the return from the stock market for the year.

Also, when the economy is in a recession, May through October typically contains the months that produce the largest losses for the Dow. During the 2008 recession, the Dow was down 27.3% between May and October but it was only down 12.4% between November and April. Likewise, during the 2001 recession, the Dow was down 15.5% between May and October but it was actually positive 9.6% between November and April.

Measure of Magnitude Not Direction

The further you dig into the data, the more it seems that the "Sell In May" strategy is a more accurate measure of "magnitude" instead of direction. Let's compare the May to October vs. the November to April return data of the Dow Jones Industrial Average 2008 – 2015 from Stock Almanac.

Looking at this time period, the losses were either less severe or the gains were greater between the November and April time frame 6 out of 8 years or 75% of the time. Compared with only 3 out of the 8 years where the direction of the returns were different when comparing those two time frames or 37.5% of the time.

Recession vs. Expansion

I think there are a number of takeaways from looking at this data. One might conclude that when U.S. economy is in a period of expansion, the "Sell In May" strategy has less than a coin flip chance of creating a more favorable investment return. However, when the economy is in a recession, the historical data may also suggest that more weight be given to the strategy since May through October in the past two recessions has contained the largest drops in the stock market.With all of that said, timing the market is very difficult and many investment professionals even label it as foolish. In general, long term investors are often better served by selecting an asset allocation that is appropriate for their risk tolerance and time horizon and staying the course.

About Michael.........

Hi, I’m Michael Ruger. I’m the managing partner of Greenbush Financial Group and the creator of the nationally recognized Money Smart Board blog . I created the blog because there are a lot of events in life that require important financial decisions. The goal is to help our readers avoid big financial missteps, discover financial solutions that they were not aware of, and to optimize their financial future.