“Why did the market go up today?” “There must have been more buyers than sellers.” That piece of circular logic is a sort of laconic joke among traders, equivalent to saying: “I have no idea.” Naturally, prices will only rise if the enthusiasm of buyers outweighs the fear of sellers. At the same time, it captures a worthwhile nugget of …

By now, most people who read about economics have heard about the empirical revolution in the field. An economist used to be someone who spun theories out of reasonable-sounding assumptions to tell stories about why the world works the way it does. Nowadays, economists still have to understand theory, but their day-to-day work involves combing through data and crunching statistics. …

Bloomberg Bank of America Corp. has been debating proposals from Chief Operating Officer Tom Montag’s subordinates to rapidly build out a European trading hub in Paris, according to people with knowledge of the talks. Montag and some of the firm’s most senior leaders recently discussed whether to alter a tentative plan to send a few hundred employees to the French …