It went below the magic figure of 17,000 that had a lot of idiots excited.
17,001 is barely different from 16,999.
It goes up, and it goes down.
BTW, it is never adjusted for inflation, so the numbers are useless.
It should also be adjusted for dividends. The choice of whether to pay dividends or do things like stock buybacks to drive up the price are often based on the current tax rates. If capital gains are taxed less than dividends the companies will use profits to try to drive up share prices rather than send the profits to the owners. A true index will not be tricked by price run-ups during those times.
Once again, stocks automatically are adjusted for inflation. That's why stocks soar in a hyperinflation; plunge during deflation. It's not that hard to understand this. Takes more money to buy a share if the currency unit is worth less.