Stocks suffered their steepest daily drop yesterday since some of the scariest months of the COVID crisis.

The big picture: Another searing inflation report is spooking investors.

Details: The S&P 500 fell 4.3%. It was the market's worst day in an awful year — and its deepest single-day decline since it suffered a 5.9% collapse on June 11, 2020.

• The broad market index is down 17.5% this year, putting it on track for its worst annual showing since 2009, when it fell a horrific 38.5%.
• Tech stocks got beaten up especially badly, with the tech-heavy Nasdaq composite falling 5.2%. It's now down 26% this year.

What we're watching: Yields on U.S. government bonds — sometimes referred to as "interest rates" — which are the real source of the stock market's pain.

• Treasury yields moved sharply higher after the inflation report hit, as investors bet that the Federal Reserve would have to keep raising the short-term rates it's been jacking up for most of the year to try to contain inflation.
• As we've written, interest rates are an almost invisible — but incredibly important — factor in determining stock prices.

The bottom line: The stock market's woes won't abate until people think interest rates can stop rising.