The tale of Paul Tucker’s own journey through the tribal world of economics illustrates the problem of silos well. He went to Cam­bridge to study mathematics and philosophy, and never set out to be an economist. He vaguely liked the idea of public service, so in 1979 he applied for a job at the Bank of England, and though he lacked an economics degree he was accepted. “In those days nobody thought that everyone had to have a Ph.D. in economics to work at a central bank,” he ex­plained. “We had people who [majored in Greek and Latin], history, and things like that.”

That reflected the particular vision of economics at that time. The root of the word “economics” comes from two Greek words: the noun oikos, meaning “house,” and the verb nemein, mean­ing “to manage.” Originally, oikonomia was considered separate from markets and trading. It referred to “the imposition of order on the practical affairs of a household,” or putting one’s “house in order,” as the anthropologists Chris Hann and Keith Hart have pointed out. Echoes of that original sense have appeared in subsequent decades: Jane Austen writes about her female characters being “skilled at economics,” while cooking and sewing classes in 20th-century American and British schools were sometimes called “home economics.”

This vision of “economics” being akin to “stewardship” influenced the development of the Bank of England in its first two centuries of existence. However, as Tucker ascended the Bank’s hierarchy in the 1990s, he started to notice a subtle shift in how economics, was perceived—and practiced. Economists started to use increas­ingly complex quantitative mathematical models to identify and make sense of economic trends. Most ordinary on­lookers had little idea how economists actually made these seem­ingly impressive predictions. The mathematical models they used were as mysterious to nonexperts as the Latin that priests spoke in the Catholic Church in Europe during its Middle Ages. To outsiders, these models seemed powerful and the economists almost priestlike.

​* * *

In 2006, to most observers, the West seemed to be experi­encing an economic golden age. Conditions seemed so upbeat that economists had christened the first decade of the 21st century the era of “Great Moderation” or “Great Sta­bility.” If you imagined that the economy was like an airplane, it was heading in the right direction, with most of the dials on the pilot’s instrument board signaling that all was well. Everyone could relax.

But there was one other economic statistic, or dial on that instrument board, that made Paul Tucker uneasy. This was the statisti­cal series called “broad money,” or M4, which showed how much cash and credit was floating around the economy.

Tucker asked some of his staff to carry out some detective work, to work out why M4 was expanding so fast. His team had told him that the main reason was a rapid increase in the amount of borrow­ing and lending by a group of entities labeled “Other Financial Corporations” in the statistics. This OFC bucket was essentially the “miscellaneous” box, where statisticians put anything that did not fit into the normal classification system. These were entities that were defined by what they were not—not banks, brokers, insurance companies, or the other entities that statisticians knew well.