What is the modern version of “supply-side” economics? The Gig Economy. Firms like Airbnb and Uber stomp on prices by injecting new supply. Airbnb has effectively added almost 20 percent to the supply of hotel rooms in major U.S. cities. Airbnb gives headaches to hotel firms, but wins applause from vacationers and from homeowners who turn their property into income-producing assets. The Gig Economy also gives headaches to government statisticians. Consider: When someone buys a new car, the Department of Commerce calls it “consumption.” But what if the buyer drives off the car dealer lot and then puts on his Uber hat? As soon as he starts shuttling passengers around town, that vehicle magically turns into “business equipment.” But nobody bothers to call the statistician in Washington. The upshot: the Gig Economy adds supply, adds convenience, trims prices, but confounds the government. When will giggers replace the confused career statisticians?