Negative bond yields have become a thing of the past this year, following a string of large interest rate rises by global central banks — everywhere, that is, except Japan.

Negative yields — which occur when bond prices climb so high that buyers holding them to maturity are guaranteed to lose money — engulfed a large chunk of the global debt market during the depth of the Covid crisis. Those sub-zero levels stemmed from huge central bank stimulus programmes, with the US Federal Reserve and several peers slashing interest rates and buying up swaths of debt in a bid to backstop pandemic-hit markets.

The total stock of negative-yielding bonds ballooned to a record of more than $18tn at the end of 2020, according to a Bloomberg index of debt trading at yields below zero. But that pile has now dwindled to less than $2tn — all of it in Japan — after the eurozone and Switzerland ended their experiments with negative interest rates in an effort to tackle inflation.