In late spring each year, I start getting emails and message board questions asking why I don’t sell my TSP stock funds and move to the TSP F (or G) Fund for the summer. After all, “everyone knows” that all the stockbrokers go to the Hamptons, volume goes way down, and the stock market loses ground during that period every year.
There are a number of variations on the adage, but they all revolve around selling near Memorial Day and buying back into the stock market after Labor Day. Calendar based strategies are always appealing, but how has this one actually played out?
From 1970 to 2017 (so let’s call that the modern stock market), the S&P 500 has been up 32 times during the summer months, and declined 15 times. So better than two years out of three the market is up during that dreaded period. I’m not saying that the market will be up during the summer in any given year, but the odds are that it will.
To be fair, stocks were up 5.8% during the up years, and down 8% during the down years, so that evens things out a bit in terms of total return. But on average the S&P 500 has gained 1% during each of those 47 summers. (Going back further, the S&P 500 averaged 2.2% from May to October from 1950 to 2017). And in 2017, the S&P 500 was up 7.4% from the beginning of May to the end of October.
But let’s stick with that 1% number. 1% doesn’t sound like very much money – that’s only a penny per dollar invested. It sounds like such a negligible sum that it might be worth sitting out the summer months just so you don’t have to worry about it.
And that brings us back to fun with math. What if I told you that in a very realistic scenario, 1% a year could turn into hundreds of thousands of dollars in your Thrift Savings Plan by the time you were ready to spend it?
To work those numbers, let’s go to our Investor.gov compound interest calculator at: https://www.investor.gov/tools/calculators/compound-interest-calculator
Once we get there we will start with $1 in current principal (to simulate being a brand new employee), $1000 monthly addition (which is probably a little high for a new employee and very low for a more experienced one), 30 years to grow (which reflects a nice long government career), an interest rate of 8% (which is fully 2% under the S&P 500’s average return during the period 1928-2016), and we will compound that 12 times per year. That gets our TSP balance to $1,490,370 after 30 years. Not bad.
Now just make one little change – turn the 8% into 9% to account for that 1% average difference between sitting out the summers and staying invested. That results in a Thrift Savings Plan balance of $1,830,758 – a difference of $430,388. And roughly 19% more than the guy who didn’t do the math.
And that is why my money doesn’t go on vacation during the summer.