THE QUANTS by Scott Patterson (page 197)

There's clear evidence that Wall Street's gluttonous demand for loans and all the fat fees that they spit out was the key factor that allowed, and encouraged, brokers to concoct increasingly risky mortgages with toxic bells and whistles such as adjustable interest rates that shot higher a few years-or in some cases-a few months-after the loan was made. Out of twenty-five of the top subprime mortgage lenders, twenty-one were either owned or financed by major Wall Street or European banks, according to a report by the Center for Public Integrity. Without the demand from the investment banks, the bad loans would never have been made.
Like crack cocaine, it was addictive, and ultimately ruinous. While the boom lasted, securitization helped Wall Street become an increasingly powerful force in the economy. The financial sector's share of the total U.S. corporate profits hit 35 percent in 2007, up from 10 percent in the early 1980's, when quants such as Brown started to arrive at the scene. Financial institutions made up one-fourth of the market cap of the S&P 500, far more than any other industry.