Because the Japanese Yen is one of the 5 reserve currencies that make up the Special Drawing Rights (SDRs) of the International Monetary Fund (IMF). It makes up

Because the Japanese Yen is one of the 5 reserve currencies that make up the Special Drawing Rights (SDRs) of the International Monetary Fund (IMF). It makes up 8% of an IMF SDR. IMF SDRs are important because all of the central banks hold a bunch of them. The Yen is not weighted higher because Japan’s debt is quite high compared to it’s GDP and Japan could try to print it’s way out of it’s debt. The Yen is not weighted lower because they’re fortune enough to be able to print their way out of their debt if need-be compared to many other countries that hold debt in non-domestically denominated currencies. That’s the best answer I can come up with.