Last October, the world's stock of negative-yielding debt hadtumbled by more than half from its record high, as investorsadjusted to the end of super-loose monetary policy. Now it'ssoaring again after the dovish pivots around the world.

The Bloomberg Barclays Global Aggregate Negative-Yielding DebtIndex has increased in value by well over $3 trillion since its lowfive months back, to $9.3 trillion Wednesday. That's still belowthe all-time record of $12.2 trillion in June 2016.

As warnings over the global growth outlook abound, bond yieldshave been in retreat. One risk-free benchmark—10-year Treasuryyields—are close to their lowest in about a year. Japan'sequivalent is back in negative territory, while that on GermanBunds is teetering on the brink—about 6 basis points above zero.Even in Australia, which hasn't seen a recession since the 1990s,10-year yields are now below 2 percent.