The stages in the rake’s progress were the junk bond explosion of the 1980s, the development of mortgage–backed securities or "pass throughs", the creation of portfolio insurance to "manage" the extra risk, and the sprouting of hedge funds to buy up the riskiest debt and sell it to wealthy speculators. Credit agencies fed the bubble by giving bonds containing "toxic waste" triple–A ratings. Morris does not decry the value of all this financial engineering. But the new investment instruments, while hugely enlarging credit facilities by spreading risk, suffered from dangerous flaws only revealed in moments of stress. A small number of institutions – global banks, investment banks, hedge funds – built an unstable tower of debt on a tiny base of real assets. So long as a cheap–money regime forestalled defaults, the tower might wobble but stay erect. A rise in interest rates from 2005 onwards brought it crashing down.