As the Dow inches closer to a new all time high, the S&P 500 is still about 1% away from a new high of its own. Part of the reason for the divergence is that the Dow has outperformed the S&P 500 by that amount year to date. However, the Dow did underperform the S&P 500 by almost 6% last year and actually has a history of underperforming the S&P 500.
Below is a chart of the historical performance of the $DJIA and the $SPX going back to 1957, the year that the S&P 500 was created. Since then the S&P 500 has outperformed the Dow by 452%, although each index has given investors solid returns. The S&P 500 is up 3390% while the Dow is up 2937%, which means that an investor that put $100k into each index in 1957 would have $3.39m vs. $2.93m. The largest performance spread between the two indices happened in the early ‘oughts when at one point the S&P 500 had outperformed the Dow by 1000%