Economist Richard Koo noted that in post-1990 Japan, the bursting of an asset bubble led to a balance sheet recession that compressed Japanese long-term government bond yields to almost zero. However, the forward earnings yield on the Nikkei rose steadily for several decades post the 1990 collapse, only falling during periods of deliberate intervention by the Bank of Japan (BOI), and only really gaining traction post-2013 when the BOJ began to directly purchase Japanese equity ETFs in large quantities. Koo explained that in Japan the rise in the earnings yield was due to a collapse in long-term growth prospects for Japanese equities (per Gordon's growth model, above), which was compounded by the dramatic rise in the value of Japanese government bonds (from the 10-year yield falling to almost zero), which "crowded-out" equities in the allocation of investor capital. By December 2020, the BOJ had become the biggest owner of Japanese equities, acquired with printed funds.