In “The Growth of Modern Finance,” Robin Greenwood and David Scharfstein of Harvard Business School show that the share of finance in US GDP almost doubled between 1980 and 2006, just before the onset of the financial crisis, from 4.9% to 8.3%. The two main factors driving that increase were the expansion of credit and the rapid rise in resources devoted to asset management (associated, not coincidentally, with the exponential growth in financial-sector incomes).