Which Day of the Week Has the Best Stock Market Performance?

August 29, 2015

I heard the following in Richard Thaler’s book Misbehaving: The Making of Behavioral Economics* the other day:

“Stocks tend to go up on Fridays and down on Mondays.”

Of course I can’t just read or hear—I was listening to the Audible version of the book—something like that and not investigate it.

In my spreadsheets, I found a copy of the daily closing prices for the Dow Jones Industrial Average going back to 1928. I updated it through Monday’s (August 24, 2015) closing price and ran the numbers. Below is what I found:

DOW JONES INDUSTRIAL AVERAGE

PERFORMANCE BY DAY OF THE WEEK
 
Down Days
Even/Up Days
Total Days
Pct. Down
Pct. Even/Up
Monday 2140 2072 4212 50.8% 49.2%
Tuesday 2116 2309 4425 47.8% 52.2%
Wednesday 2042 2406 4448 45.9% 54.1%
Thursday 2080 2298 4378 47.5% 52.5%
Friday 1986 2374 4360 45.6% 54.4%
TOTALS 10364 11459 21823 47.5% 52.5%

That information wasn’t enough for me. I also wanted to see the average performance for down days, up days, and for all days based on the day of the week. Here are those results:

DOW JONES INDUSTRIAL AVERAGE

 
Avg. Down Day
Avg. Even/Up Day
Avg. Day
Monday -0.88% 0.78% -0.06%
Tuesday -0.72% 0.74% 0.05%
Wednesday -0.73% 0.74% 0.07%
Thursday -0.71% 0.70% 0.03%
Friday -0.73% 0.69% 0.04%

So, while what Thaler says is true, Wednesday is the best day of the week performance-wise (these are price returns).

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