The S&P 500 crossed the 4,000 mark on Thursday, a little over a year after the index hit its pandemic low.

Why it matters: Stocks don't only go up. From a peak of 1,552 at the height of the dot-com bubble in 2000, the S&P 500 dropped to a low of 667 in 2009, at the worst point of the financial crisis. Since then, however, the strength of the stock market's 12-year ascent has astonished investors and market strategists.

• Thursday's milestone represents a near doubling of the index since the start of the coronavirus pandemic in March of last year, when the index hit a low of 2,192.

The big picture: The S&P 500 is accelerating, hitting milestone markers more quickly.

• The index hit 3,000 mark for the first time ever as recently as in July 2019. It has taken less than seven years to double after reaching the 2,000 mark in August 2014.
• By contrast, it took the index more than 16 years to double from the 1,000 point mark, which it first hit in February 1998.