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September Seasonality Barometer

Seasonality has been the subject of numerous academic and professional investment studies. Some of the more popular seasonality trends include (1) Sell in May and go away; (2) Summer Rally; (3) the January Indicator, and (4) the October crash month barometer.


Seasonality often refers to a particular timeframe where stocks, sectors, market indices are subject to and influenced by recurring tendencies that produce reliable trends. Tendencies refer to weather conditions (winter vs summer, fall vs spring, and year-end vs the beginning of the year) and calendar events (end of the month/quarter/year vs the beginning of the month/quarter/year).


So, is there also a September barometer?


Labor Day, is a US national holiday typically held annually on the first Monday of September. This year, Labor Day this year arrives on Monday, 9/7/20, or well into the start of September. Nonetheless, Labor Day marks the end of the summer and the beginning of fall. For many, this is the start of another school year. And for many others, it is the end of vacations and the start of the business year.


For the first half of the century, September has been a consistent and often reliable leading barometer month as it relates to being the biggest percentage loser on both the S&P 500 Index and the Dow Jones Industrial Average. September remains one of the weakest months of the year.


It is often accompanied by lackluster stock market returns and an increase in market volatility. The beginning of September or the days before and after Labor Day tend to be more favorable than at the end of the month. The discrepancy in performance is probably due to the end-of-quarter portfolio restructuring and window-dressing activities.


This year is also another important Presidential Election Year. Some believe it will be a game-changer that will have an impact on investors, consumers, savers, retirees, college students, and many others. Whether we will experience a repeat of prior election year tendencies heading into September and October of an election year, it is worthwhile to remember the immediate months before the election tend to be extremely volatile for investors.


Although the stock market has an inherent long-term upward bias (bull trend), and September and October tend to rise more often than not, investors tend to be increasingly nervous during this timeframe. There is a collective sigh of relief once the election has passed as the stock market rallies strongly toward the end of the year.

Enclosed below are brief seasonality statistics on the average returns for key US stock indexes during September over the past 20-years. Also, are the average returns for September during the past 4 US Presidential Elections (2016, 2012, 2008, and 2004).


S&P 500 Index (SPX – 3,580.84)


-0.5% September average return over the past 20-years (2001-2020)

-1.5% September average return during the last 4 US Presidential Election Years (2016, 2012, 2008, and 2004)


Dow Jones Industrial Average (INDU – 29,100.50)


-0.5% September average return over the past 20-years (2001-2020)

-1.2% September average return during the last 4 US Presidential Election Years (2016, 2012, 2008, and 2004)


NYSE Composite Index (NYA – 13,276.74)


-0.5% September average return over the past 20-years (2001-2020)

-1.4% September average return during the last 4 US Presidential Election Years (2016, 2012, 2008, and 2004)


Nasdaq Composite Index (COMPQ – 12,056.44)


-0.6% September average return over the past 20-years (2001-2020)

-1.3% September average return during the last 4 US Presidential Election Years (2016, 2012, 2008, and 2004)


SPX monthly average returns in the last 20 years Source: Courtesy of StockCharts.com

SPX monthly average returns in the last 4 US Presidential Elections Source: Courtesy of StockCharts.com

SPX chart during the last 4 US Presidential Elections (2016, 2012, 2008, and 2004) Source: Courtesy of StockCharts.com

INDU monthly average returns in the last 20 years Source: Courtesy of StockCharts.com

INDU monthly average returns in the last 4 US Presidential Elections Source: Courtesy of StockCharts.com


INDU chart during the last 4 US Presidential Elections (2016, 2012, 2008, and 2004) Source: Courtesy of StockCharts.com

NYA monthly average returns in the last 20 years Source: Courtesy of StockCharts.com

NYA monthly average returns in the last 4 US Presidential Elections Source: Courtesy of StockCharts.com

NYA chart during the last 4 US Presidential Elections (2016, 2012, 2008, and 2004) Source: Courtesy of StockCharts.com

COMPQ monthly average returns in the last 20 years Source: Courtesy of StockCharts.com


COMPQ monthly average returns in the last 4 US Presidential Elections Source: Courtesy of StockCharts.com

COMPQ chart during the last 4 US Presidential Elections (2016, 2012, 2008, and 2004) Source: Courtesy of StockCharts.com

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