The last inversion of this part of the yield curve was in December 2005, two years before a recession brought on by the financial crisis hit.
A recession occurs, on average, 22 months following such an inversion, according to Credit Suisse.
The yield on the benchmark 10-year Treasury note broke below the 2-year rate early Wednesday, an odd bond market phenomenon that has been a reliable, albeit early, indicator for economic recessions.
The yield on U.S. 30-year bond also turned heads on Wall Street during Wednesday's session as it fell to an all-time low, dropping past its prior record notched in summer 2016. The two historic moves coming in tandem show that investors are increasingly worried, and indeed preparing for, a slowdown in both the U.S. and global economies.
Earlier Wednesday, the yield on the benchmark 10-year Treasury note was at 1.623%, below the 2-year yield at 1.634%. In practice, that means that investors are better compensated for loaning the U.S. over two years than they are for loaning for 10 years. The yields steepened later in the session, pushing the 10-year rate back above that of the 2-year note at 1.58%.