Such market optimism led to de-regulation of financial markets in the 1980’s and 1990’s, and the subsequent explosion of financial innovation which made it “safe” to borrow larger and larger sums of money on the back of predictably rising assets. The just-collapsed credit bubble, fueled by so-called special investment vehicles, derivatives, collateralized debt obligations, and phony triple-A ratings, was built on the illusions of mathematical modeling.