Production costs in many shale-gas plays exceed current gas prices, and maintaining production requires ever-increasing drilling and the capital input to support it. SHALE GAS Two technologies - horizontal drilling coupled with large-scale, multi-stage hydraulic fracturing (fracking) - have made it possible to extract hydrocarbons trapped in impermeable rocks (see Nature 477, 271-275; 2011). Existing production histories are a few years at best, and thus are insufficient to substantiate such long lifetimes for wells. Because production declines more steeply than these models typically suggest, the method often overestimates ultimate recoveries and economic performance (see go.nature.com/kiamlk).