interest bonds "to maturity"...as the attached article notes...that was a risky strategy...
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But underlying the failure was a demonstrable problem, one to keep an eye on for other banks: The company had invested its deposits in low-interest rate bonds that it held on its books on a long-term “hold-to-maturity” basis. That means that it did not have to mark-to-market those bonds until they were sold, leaving investors with a somewhat distorted view of its balance sheet. So long as a bank doesn’t need to sell “hold-to-maturity” assets to meet withdrawal requests, there is no problem. But if a bank has to sell at a loss, that’s when things get complicated.
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"Risk" can come from many directions...
Also, their clientele (many hedge funds with large stakes) is very astute, attentive and quick to act with 'internet speed'...they sensed a problem and withdrew funds "rapidly".
Link: https://deal.town/the-new-york-times/dealbook-why-did-silicon-valley-bank-collapse-P3W3QNLK9