At the end of the last century, Japan became the first major economy to cut interest rates to zero.
During the Covid pandemic, many other nations adopted that tactic to support their economies.
Those countries are now raising interest rates but the Bank of Japan (BOJ) on Friday yet again kept its main rate below zero. And that is bad for its currency.
The yen has long been seen as a safe haven, which investors traditionally bought at times of crisis.
But that status is now on shaky ground. This year alone it has lost more than a fifth of its value against the US dollar to hit the lowest level since 1990.
Why is this happening?
The yen’s slide has been driven by the difference between interest rates in Japan and the US.
Since March, the US Federal Reserve has aggressively raised its main interest rate – from 0.25% to 3.25% – as it tries to tackle the rising cost of living.
Higher interest rates tend to make a currency more attractive to investors.
As a result there is less demand for currencies from countries with lower rates and those currencies fall in value.
-BBC