Treasury market inflation expectations remain close to the lowest level since February, when economic worries were elevated. The yield spread for the nominal 10-year Treasury Note less its inflation-indexed counterpart was unchanged yesterday (June 22) at 1.43%, based on daily data via Treasury.gov. That’s near the lowest level since February—a sign that the bond market is cautious on the outlook for the US economy. Or is it a byproduct of temporary Brexit fears, which may or may not lift after tomorrow’s referendum in the UK that will decide if Britain remains in the European Union? Whatever the source of the downside bias in Treasury inflation expectations of late, the soft trend contrasts with the recent rebound in the US stock market, which implies that any macro worries are exaggerated for the world’s largest economy.

The relatively upbeat mood in equities contrasts sharply with the recent decline in the Treasury market’s inflation forecast. Recent history shows that the two generally track each other, and so the latest divergence may be a sign that old relationship, which has prevailed for much of the post-2008 era, is giving way to, well, something else that has yet to emerge in clear and definite terms.

It’s reasonable to put deeper analysis on hold until we learn the outcome of Thursday’s Brexit vote, which may or may not have implications for the Eurozone and the US as well as for Britain.

“A U.K. vote to exit the European Union could have significant economic repercussions,” Fed Chair Janet Yellen said in yesterday’s testimony in Congress. Nonetheless, she put a positive spin on the outlook, opining that “the FOMC continues to anticipate that economic conditions will improve further and that the economy will evolve in a manner that will warrant only gradual increases in the federal funds rate.”

Maybe so, but if already low Treasury market inflation expectations fall further in the days and weeks ahead, the case for optimism will come under increasing pressure.

As for the widening spread between US stocks and the market’s inflation forecast, history suggests the gap will close. The only question: will equities or Treasuries cry “uncle”?