The S&P 500 over the past 20 years has averaged a near 1 percent gain in the week following the federal tax filing deadline and has been higher 75% of the time, according to Bespoke Investment Group. By the second week after April 15, the S&P has been up 1.5% and was higher 75% of the time.
The positive pattern did not work out after tax day in 2018, when the S&P lost 2.9 percent in the week after April 15, its worst one week post-tax day return since 1990. In the past 20 years, the worst performance was in 2002 when the S&P was down 3.4 percent after the second week.
The best performance was in 2001, when the S&P was up 3.8% after one week and nearly 6% after two weeks.
"April seasonally is a strong month. You get increased spending from the refunds coming through, but its more of just a seasonal phenomena," said Paul Hickey, co-founder of Bespoke. "Aprils a real strong month. Its the end of the six month stretch, where returns tend to be positive."
Right after April comes the "sell in May and go away" period for stocks. Thats May through October when the market does not do as well as the previous six months. For instance, the Dow was down 0.6 percent on average in the period May 1 through Oct. 31, going back to 1950, according to the Stock Traders Almanac. In the Nov. 1 to April 30 period over the same years, the Dow gained an average 7.5%.
"April is a little tricky. Its when earnings generally start to come out," Hickey said. "The Q1 reporting period has historically yielded positive returns for stocks." He also said there were a good number of downward revisions to first quarter earnings.
"Negative revisions have historically been good for stock market gains," he said, noting companies tend to have a lowered bar to beat.