Dow, at least as far as I know. I wish there was one.
I keep track of the S&P 500 stats on a daily basis on the pinned post https://www.democraticunderground.com/111699775
which includes percentage changes from election day, from pre-inauguration day close, from the all-time-high, and year-to-date. (I also have a bottom section on the Dow to make the Dow people happy.)
A couple of stats of interest:
S&P 500 is down 16.0% from it's Feb 19 all time high
Dow is down 15.2% from it's Dec 4 all time high
Neither have reached bear market territory yet, which is 20% down. I expect they both will in days or a few weeks.
Re: another comment -- something like 55% of U.S. households own stocks or stock funds. So while it might not be "the economy", it, and bonds, are the retirement nest eggs for many Americans (along with home ownership). And the stock market is one of the Conference Board's leading economic indicators, as most recessions are preceded by sizable market downturns. When stocks are in a long dive, a lot of people and businesses cut back on their spending and that affects everyone, not just stockholders. Also insurers' assets are reduced, pushing them towards raising premiums. And pension funds are hurt.
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