The combined market cap of the Dow 30 companies is about $4.25 trillion, while the combined value of the 500 companies in the S&P more than triples that figure to nearly $14 trillion. Most exchange traded funds are tied to the S&P or sectors within it, not the Dow. So why do we hold onto this fascination with the DJIA?
"We've had it since the 1890s, it's historic," said Kaplan. He added that these 30 companies remain a pretty good measurement of the health of the U.S. economy. "I don't think they reflect the economy as well as the top 500, but, listen, any time you pick the top 30 data points, it gives you a pretty good indication."
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The two indices move in tandem, but not exactly. What's a good analogy? How do you compare them?
Remember those SAT questions, "A is to B as C is to D"? Let's be creative. Here are my suggestions for comparing the Dow to the S&P 500.
The Gilligan Factor
If the Dow is sexy Ginger, the S&P is dependable Mary Ann. (Google this one kids, it's a debate that's been raging far longer than Edward vs. Jacob.)
The Dow is like a frothy tall latte, while the S&P is a mega extra-large "trenta" black coffee.
The Dow is an aircraft carrier, the S&P is the entire fleet.
The Dow is Capt. Kirk (flashy), the S&P is Capt. Picard (capable).
The Dow is A-Rod, the S&P is Jeter.
I could go on and on ... Dow v. S&P is like:
Apple vs. Amazon
Oscars vs. Golden Globes (includes TV!)
Boxers vs. Briefs
And my favorite:
Aragorn vs. Frodo. Yes, Aragorn reveals himself to be a king in "The Lord of the Rings," but lowly Frodo saves Middle Earth. In other words, Aragorn is Alcoa, and Frodo is ... Google.
Work with me here.
—By CNBC's Jane Wells; Follow her on Twitter: