Twice Is A Coincidence, But What About Three Times?

Happy weekend, everyone. Are you excited for Spring Break next week? I know I am. I'm looking forward to a long, relaxing week with plenty of time for sleeping...even though I do a lot of that anyway nowadays. :) That's right, next week, I won't be updating this blog. But don't worry, I'll be back the following week!

Ahem. Ok, back to the point of this post. Yesterday, I showed that the price data for Nasdaq over the past year has a dominant period of about 128 days. That led me to wonder what the periods of other indices' prices were. So, over the course of the week, I analyzed two other indices: the Dow Jones Industrial Average, and the S&P 500, in the same manner.

First the Dow Jones, an index that measures how large, public U.S. companies have traded during a standard trading session. (Ticker Symbol: DJI) It is influenced not only by economic and corporate reports, but by domestic and foreign policy issues. Its components trade on both the NYSE Euronext and the NASDAQ OMX stock markets.

Here's the graph of its past year prices:

And from this data, I can find its period to be 128 days, just like Nasdaq's. Um, alright.

Moving on, I do the same for the S&P 500, which measures the market capitalizations of 500 leading companies publicly traded in U.S. stock markets. It covers about 75% of U.S. equities and is considered by many to be the best representation of the welfare of the U.S. economy. 

Its graph:

And its period turns out to be...128 days again! 

Hmm, so the Nasdaq Composite, DJ Industrial Average, and S&P 500 all have the same period? Coincidence? I think not!