Many types of institutions have to mark to market on a ~constant basis, so it's not impossible. Yes there are certain asset classes (private companies, for exam

Many types of institutions have to mark to market on a ~constant basis, so it's not impossible. Yes there are certain asset classes (private companies, for example) that don't have easy or reliable marks (but people still do it anyway!). But at least for SVB the issue was not determining the market value, but that the market value was bad.