The world remains awash in $10.4 trillion of negative-yielding debt, a level that Fitch Ratings warns poses a substantial threat to investors.
Since central banks in Europe and Japan pushed sovereign yields into negative territory, the dollar level of bonds with sub-zero yields grew at one point to nearly $12 trillion.
Though that number's come down recently, Fitch said Thursday that dangers remain.
"While the outstanding amount of negative yielding sovereign debt declined in recent months, the persistence of low and negative yielding debt globally will continue to take its toll on investors, particularly buy-and-hold investors such as insurance companies," Jonathan Boise, associate director of macro credit research at Fitch, said in a report.
The total is below the $10.9 trillion reported Sept. 12, thanks largely to a decline in Europe, which saw a $450 billion drop over the time period. Italy also has seen a considerable decline, from $480 billion to $340 billion, which Fitch attributes to political jitters ahead of a constitutional referendum in December.
However, some damage already has been done.
Fitch pointed to an example: A 30-year German bond that matured on Sept. 20 had a 5.625 percent coupon. That same bond purchased on Nov. 1 would provide a 0.8 percent rate. Coupons are the semiannual payments that bondholders get for their investment.
"For investors that have not realized gains on bond prices, income generated by their portfolios will continue to diminish in an ultra-low rate environment," Boise said.
Japan leads the world in negative-yielding debt with $6.9 trillion, though that number has stabilized since the central bank there announced it would target a zero yield on its benchmark 10-year bond.