Wall Street has many traditions and proverbs, and many investors still pay close attention to them. One commonly quoted rule in spring is that investors should "sell in May and go away," selling their stock market investments and only buying them back in November. The idea behind this rule is that when you look at stock market history over the past 90 years, two of the three worst months come in May and September, while three of the four best months for the market come in December, January, and April.