答案在The Economist May 7th 2022 Finance & economics 中“Quantitative tightening---Braced for impact” 这篇文章末段可以找到。

The Economist May 7th 2022 Finance & economics

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idiom

come of age 到达法定年龄，成年，成熟，发达

同义词： reach adulthood, mature, develop, grow up

试译下这段吧：

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.

考虑一下国库券或债券的有效期。通常每周有一到两次，就有一批新国债形成。简而言之，新国债的第一个家通常是投资银行的交易台。这些交易员可能会为自己保留一些，但一般来说，他们会将大部分分配给更多的永久持有者，如共同基金、外国政府或公司或美联储的债券投资组合。有一部分会反复换手——每个工作日约有7,000亿美元的交易量——但许多人将终生按兵不动。新国债的有效期通常会预先确定：即它们在形成后短至一个月或长达30年到期或“成熟”，到那时它们就会被结算，不再存在。

出处：头条号 @Imprint of Learning