The graph above shows how Treasury security holdings by the banking sector and the Treasury yield have evolved over the past five years. The red line shows the Treasury and agency securities that commercial banks hold as a share of their total assets since mid-2018. The green line shows the market yield on 10-year Treasury securities over the same period.
This relationship between market yields and bank holdings seems to be divided into three distinct phases:
In the period before the pandemic-related recession, which began in February 2020, these lines seem to have a slight inverse relationship: Treasury holdings trended up while the Treasury yield declined.
In the two years after the recession began, both lines increased together after a brief initial dip.
In the past year, nearly three years since the pandemic recession ended, the inverse relationship reappears, with Treasury holdings trending down and Treasury yields increasing.
One can understand these three phases as an interplay between demand and supply.