The Fed’s balance-sheet is about to shrink. Wall Street is not ready

CONSIDER THE life of a Treasury bill or bond. Typically once or twice a week, a batch of fresh Treasuries are born. Their first home is usually, briefly, an investment bank's dealing desk. Those dealers might hold on to a few for themselves, but generally they distribute the bulk to more permanent owners, like the bond portfolios of a mutual fund, a foreign government or a company or the Federal Reserve. A certain slice will swap hands repeatedly—some $700bn or so are traded each business day—but many will stay put for their lifetimes. Their deaths are predetermined: they come of age, or “mature”, as little as one month or as long as 30 years after their birth, at which point they are settled and cease to exist.