Stock market scare as Dow drops 460 points before slight rebound

NEW YORK (CNNMoney) -- It's another "look out below" day in the stock market.

The Dow plunged as much as 460 points Wednesday afternoon before pulling back a bit, although a 370 point loss isn't anything to cheer. There wasn't an obvious trigger. Ebola and 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.

If the afternoon's steep losses hold, the S&P 500 and Nasdaq will also end the day in the red for the year.

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 9.5% since then. That's rough, but it's not quite 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 afternoon, the S&P is hovering around 1,830.

(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 -- and it's getting to gale force wind levels.

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. As of Tuesday afternoon, the VIX was at about 25. That's a lot higher than the 12 to 13 it was at a month ago.

The unofficial alarm bell is the 30 mark, which the VIX crossed Wednesday afternoon.

3. Investors are putting money into bonds. It's debatable whether it's a 'freak out'

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 several times, although it is on track to close just above the 2% mark.

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 2pm ET.