Over the next two decades, it fell 82 percent. Twenty-seven years later, it is still only at less than half that 1989 value. Property values crashed along with share prices, which turned large parts of the financial system into zombie banks — meaning banks that hold so many bad assets that they are essentially broke, which means they can’t lend money and therefore cease to fulfill one of a bank’s central roles in the modern economy, which is to help keep the flow of credit moving.