The bond market smells a recession. On Friday, stock investors caught a whiff, too.

Economic forecasters and Wall Street traders have been watching for months as interest rates on long-term United States government bonds have dropped toward the rates on short-term debt.

Investors normally demand higher yields to buy longer-term bonds, and when those long-term yields decline it can signal a slowdown in economic growth.

On rare occasions , long-term yields can actually fall below yields on short-term bonds — a “yield curve inversion” in the parlance of the markets. Such unusual occurrences have preceded every recession over the last 60 years.

And it happened on Friday.

The inversion followed a sharp decline on yields on long-term Treasury bonds this week after the Federal Reserve decided on Wednesday to leave interest rates unchanged and signaled that it was unlikely to raise rates through the end of 2019.