An account of why risk management failed
“There was a willful designing of the systems to measure the risks in a certain way that would not necessarily pick up all the right risks,” said Gregg Berman, the co-head of the risk-management group at RiskMetrics, a software company spun out of JPMorgan. “They wanted to keep their capital base as stable as possible so that the limits they imposed on their trading desks and portfolio managers would be stable.”
One way they did this, Mr. Berman said, was to make sure the computer models looked at several years of trading history instead of just the last few months. The most important models calculate a measure known as Value at Risk — the amount of money you might lose in the worst plausible situation. They try to figure out what that worst case is by looking at how volatile markets have been in the past.
But since the markets were placid for several years (as mortgage bankers busily lent money to anyone with a pulse), the computers were slow to say that risk had increased as defaults started to rise.
It was like a weather forecaster in Houston last weekend talking about the onset of Hurricane Ike by giving the average wind speed for the previous month. [Emphasis added.]
My late father used to say, "To err is human, but to really screw up, you need a computer."