The Dow shattered through the 17,000-mark Thursday for the first time ever. So far this year, however, the index has been left behind.
Year-to-date, the S&P 500 is up 7 percent, while the Dow is up 3 percent.
Although the two indexes are calculated differently—the Dow being a price-weighted index and the S&P 500 a capitalization-weighted one, the first-half divergent performance appears to be more the exception than the rule.
Historically, there have been only seven other instances when the S&P outperformed the Dow by over 4 percent going into the second half of the year.
The few times the S&P outperformed the Dow in the first half of the year, the Dow returned the favor by closing the gap, and outperforming the S&P in the second half.
In fact, if you exclude the market's devastating performance in the second half of 1931 when both indexes lost over 45 percent, the average gain for the Dow in the second half is over 6 percent compared with 2 percent for the S&P.