"In the familiar twentieth-century island model of international economic interaction, the basic units were national economies that traded with one another, ran trade surpluses and deficits and accumulated national claims and liabilities. Those entities were made familiar by economists, who gave them an empirical, everyday reality in statistics for unemployment, inflation and GDP. And around them an entire conception of national politics developed. Good economic policy was what was good for GDP growth. Questions of distribution—the politics of “who whom?”—could be weighed up against the general interest in “growing the size of the cake.” By contrast, the new macrofinancial economics, with its relentless focus on the “interlocking matrix” of corporate balance sheets, strips away all the comforting euphemisms. National economic aggregates are replaced by a focus on corporate balance sheets, where the real action in the financial system is. This is hugely illuminating. It gives economic policy a far greater grip. But it exposes something that is deeply indigestible in political terms. The financial system does not, in fact, consist of “national monetary flows.” Nor is it made up of a mass of tiny, anonymous, microscopic firms—the ideal of “perfect competition” and the economic analogue to the individual citizen. The overwhelming majority of private credit creation is done by a tightknit corporate oligarchy—the key cells in Shin’s interlocking matrix. At a global level twenty to thirty banks matter. Allowing for nationally significant banks, the number worldwide is perhaps a hundred big financial firms. Techniques for identifying and monitoring the so-called systemically important financial institutions (SIFI)—known as macroprudential supervision—are among the major governmental innovations of the crisis and its aftermath."