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100 years of stock market gains and losses, visualized

This post comes via Know More, Wonkblog's social media site.

Are there good and bad days to play the stock market? Unfortunately no one can predict this for the future, but we can analyze what happened in the past.

Seth Kadish, a data scientist who runs the blog Vizual Statistix, used roughly 100 years of data – from Jul. 30, 1914 to Jan. 26, 2015 – to chart the daily percentage change in closing price for the Dow Jones Industrial Average. He then binned this data together by day of the year and created the heat map below.

The blue cells in the map signify market gains, while the orange cells indicate losses. White boxes are dates that don’t exist or fixed-date holidays when the market is closed, like Christmas and New Year’s Day. The table on the left shows the percentage of time a given day increases, while the table on the right shows the median percent change for each date.

A few trends emerge. Apr. 15, tax day, has been a particularly good day for the stock market historically, as are some dates around national holidays: Jul. 3, Dec. 24 and 26, and Jan. 2. The worst days include Apr. 7 and Feb. 29 (which only occurs every four years, and thus has less data overall).

Kadish notes that this graph is for entertainment purposes only, not for creating investment strategies -- obviously the stock market's day-to-day performance can vary significantly from the historical average.

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