Why? This is a compelling question without, as yet, a compelling answer. Indeed, so far as I can tell, economists have not engaged in rigorous self-criticism to explain their lapse. We've had some casual theories and some partisan recriminations: "Free-market ideology" is a standard scapegoat on the assumption that most economists are "free-market ideologues." But that's not true. In any case, the crisis surprised liberal and conservative economists, Republicans and Democrats alike.
This brings us back to Ferguson. The creation of money was a seminal historic event; so was the subsequent invention of finance -- the saving and investing of money. Without them, we could never have moved beyond barter to a modern economy based on specialization and building for the future. But these advances came interwoven with bubbles, crashes, swindles and hyperinflations. Finance has been a wellspring of both progress and instability.
Ferguson is an able guide. He relates the creation of the bond market by Italian city-states in the 14th century as a way to finance their wars against each other; he explains the South Sea and Mississippi "bubbles" in England and France around 1720 -- stock market manipulations based on fantasized riches in the New World; and, finally, he visits the recent housing bubble.
Ferguson's breezy tour suggests two reasons the present crisis embarrassed most economists. The first involves finance itself. The crisis originated in financial markets (the markets for stocks, bonds and many complex securities), and yet finance occupies a peripheral position in mainstream economics. It's studied by a subset of economists, and financial markets -- their ups, downs and side effects -- are not considered big sources of economic expansions and slumps. Economists tend to focus directly on the spending of consumers, businesses and government. It was also widely assumed that deposit insurance and the existence of the Federal Reserve would prevent financial panics.
Well, if you de-emphasize financial markets and financial markets are decisive, you're out to lunch. Financial markets pumped up the real estate bubble; greater housing and stock market wealth inspired a consumer spending boom; losses on "subprime" mortgage securities triggered a collapse of confidence. Some economists have grudgingly, if obscurely, conceded error. A study by the International Monetary Fund called "Initial Lessons of the Crisis" admits: There "was an under-appreciation of systemic risks coming from . . . financial sector feedbacks onto the real economy." That's an understatement.