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June is the last month of the second quarter, and it's also a month when we're in the earnings "off-season" period. The first part of earnings season each quarter typically starts in the first half of the first month of the quarter, and it runs through the middle to late part of the next month.We wanted to see how the stock market has performed since 1990 if you only owned it during the first, second, and third month of each quarter. We used 1990 as our starting point for the "modern" earnings reporting structure since that aligns with the launch of CNBC in 1989.As financial media spawned in the early 1990s, quarterly earnings reports began providing plenty of regular content to share with viewers. Since earnings ultimately drive returns, it would make sense if market performance has historically been stronger during the months encompassing earnings season rather than the earnings off season.

The results since 1990 generally support this view.As shown below, if you only owned the S&P during the first month of each quarter, you'd be up 370.2%.If you only owned the index during the second month of each quarter, you'd be up 143.6%. And if you only owned during the last month of each quarter, you'd be up just 46.1%. Strong performance in the first month of each quarter could also be driven by institutional inflows.Whatever the case, owning during the first month of the quarter has led the other two for the last 25 years, and it has really done well since the Financial Crisis in the late aughts (although it's been flat for the last couple of years). Additionally, the middle month of the quarter has been very strong since early 2023.C ould this be due to NVIDIA (NVDA), which always reports in the second month of earnings season and has exploded in value during the current AI Boom?

Finally, only owning during the last month of the quarter (March, June, September, and December) has essentially been a flat trade since the late 1990s.

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