It’s a truism that good decision makers should look before they leap. But good decision makers should also look back after they leap, to see how far they moved and in what direction. Only by looking back can they know if they are on course and whether they need to leap again. Over the last thirty years, the look-before-you-leap principle has become a fixture in the federal regulatory process. Before regulatory agencies like the Food and Drug Administration and the Department of Commerce can adopt significant rules, they must produce detailed regulatory impact analyses that force decision makers to think carefully about the costs and benefits of their proposed actions. They must also have their benefit-cost analyses reviewed by the Whit...