You will recall David Li, the quant who devised the formula that "revolutionized" derivatives. I believe this post from Robert Oak was the last time he was discussed at EP.
Now, along comes this article recently published in FT. While it doesn't shed any new light on the formula, per se, it is a very interesting biographical piece about young Mr. Li. It also retraces key developments in the creation and the ascendancy of quantitative analysis on Wall Street.
In the autumn of 1987, the man who would become the world’s most influential actuary landed in Canada on a flight from China. Neither Xiang Lin Li nor the handful of fellow junior academics with whom he was travelling – all from the University of Nankai – had ever been abroad before, yet they had come at the behest of the Chinese and Canadian governments to do something most unusual: study capitalism. The small band of mathematicians and statisticians would be taking business degrees at Quebec’s Laval University.
After graduation from Laval, he enrolled at a new university, Waterloo, near Toronto. He would now be studying actuarial science. And this wasn’t the only change: the move from genteel, francophone Montreal to the more worldly and business-oriented Toronto was profound – and deliberate. According to Jie Dai, a fellow immigrant from China and a classmate at Laval, “I clearly remember [Li] mention that if you are an actuarial guy, you can earn a lot of money.”
But, of course, the really big money was on Wall Street and that is where David Li ended up in 1998.
Li had come to New York to work for a consultancy called the RiskMetrics Group, which had been spun out of JP Morgan, but he was still thinking about life, death and love. In 2000, he published a paper in the prestigious Journal of Fixed Income that gained some serious attention. In it, Li performed a most elegant trick. Borrowing from his work in actuarial science and insurance and his knowledge of the broken-heart syndrome, he attempted to solve one of Wall Street quants’ most intractable problems: default correlation.
Li realised that his insight was groundbreaking. Speaking to The Wall Street Journal seven years later, he said: “Suddenly I thought that the problem I was trying to solve [as an actuary] was exactly the problem these guys were trying to solve. Default [on a loan] is like the death of a company.” And if he could apply the broken hearts maths to broken companies, he’d have a way of mathematically modelling the effect that one company’s default would have on the chance of default for others.
It's a really good piece of reading for a Sunday afternoon in the springtime. When I read this kind of story, I think of the movie Sliding Doors. What would the world be like today if David Li had stayed in his small Chinese village?