The Dow plunged as much as 370 points Wednesday morning before pulling back a bit, although a 150 point loss isn't anything to cheer. There wasn't an obvious trigger. Ebolaand Europe's sour economy are clearly worrying. Earnings have been so-so, and retail sales data out this morning was disappointing.
October has been a brutal month, erasing most of the 2014 stock market gains. The Dow is negative for the year, and CNNMoney's Fear & Greed Index is showing extreme fear.
Most investors are better off not obsessing about the day to day market moves.
But if you're keeping an eye on the numbers, here are three critical stats to watch. There is no "magic number" that triggers a sell-off, but these indicators would be big red flags.
1. We're near a correction, but not there yet
Only a month ago, the S&P 500 index closed at an all-time high of 2,011. At its worst point Wednesday morning, the index was down around 8.7% since then. That's rough, but it's not the 10% drop that would constitute a true correction, let alone the 20% drop that would signal a bear market.
Keep an eye on this number: 1,810. If the S&P 500 slips below that, we're in a correction. As of Wednesday morning, we were around 1,850.
(For those who like numbers, at the nadir of the financial crisis in March 2009, the S&P 500 closed below 700).
2. Volatility is back, but it's still a breeze, not a gale force wind.
The VIX volatility index is currently at about 23.Most days the stock market moves a little bit higher or lower. For instance, the S&P 500 moved less than 0.2% on Tuesday. But since the end of October, the stock market has had numerous "wild swings" where it shifts more than 1% (or even more than 2% in some cases).
That's referred to as volatility. The VIX Index is the main measure of volatility. It has spiked about 90% in the past month -- a huge jump. But even so, the VIX currently stands at about 26 (it hit as high as 28 Wednesday morning). That's a lot higher than the 12 to 13 it was at a month ago, but it's yet to hit the 30 mark, which is the unofficial alarm bell.
3. Investors are putting money into bonds, but it's not a total freak out yet
When investors get scared, they don't run to mom, they run to bonds, especially U.S. government bonds. The yield on the 10-year Treasury is a good indicator of just how many people are seeking the safe arms of the bond market.
When the yield falls, you know people are gobbling up bonds.
In the middle of September, the yield on the 10-year Treasury was around 2.6%. On Tuesday it was at 2.2%. That's a quick drop, but the real indicator of a meltdown would be for the yield to drop to 2% or even below.
Sure enough, on Wednesday, the yield fell below that mark briefly, but it has since moved back above the 2% level.
The last time that happened was in 2012 when Europe was in the midst of a debt crisis and America's economic recovery was looking uncertain.
Market jitters are back, but we're not quite at a "correction" yet.
Editor's note: This story was updated Wednesday at 10am ET.
Authored by Heather Long via cnnmoney.com.