The world’s stockpile of negative-yielding debt has swelled to a fresh record in a sign that demand for havens is just as intense as that for riskier assets.

The market value of the Bloomberg Barclays Global Negative Yielding Debt Index rose to $18.04 trillion on Thursday, the highest level ever recorded. Spanish 10-year bonds were the latest to join the club, with rates sliding below 0% for the first time Friday.

About $1 trillion of bonds have seen their yields turn negative this week, meaning 27% of the world’s investment-grade debt is now sub-zero. Thanks to the slew of global issuance in 2020 as governments and companies wrestle with the impact of the coronavirus, that remains below the 30% peak reached last year.

Despite optimism about a global economic recovery next year sparking a rush to riskier assets like stocks and corporate debt, continued monetary support from central banks and concern about the relentless spread of the coronavirus has maintained investor interest in sovereign bonds. The rise in negative-yielding debt since March has coincided with a broadly weaker dollar.

Bond bulls got a boost on Thursday when the European Central Bank boosted its asset purchase program by an additional 500 billion euros ($607 billion) in a bid to support the region’s economic recovery. Meanwhile, both Australian bills saw sub-zero yields at auction for the first time, while Portuguese 10-year bond yields also dropped below 0% this week.

U.S. Treasury yields remain some of the few developed bonds still holding above 0%. In the euro area’s main debt markets in 10-year instruments, only Italian and Greek securities are trading in positive territory.

-With assistance from Sid Verma.

This article was provided by Bloomberg News.