In finance, the problems with nudging reveal it may even have a dark side. Nudgers are quick to push workers toward retirement savings, but sometimes are not doing enough to warn them about possible risks. The think tank Dēmos estimates that, over a lifetime, retirement-account fees “can cost a median-income two-earner family nearly $155,000.” John Bogle, an investor, has noted that a 2 percent fee applied over a 50-year investing lifetime would erode 63 percent of the value even of an account with healthy returns. As Bogle puts it, “the tyranny of compounding costs” is overwhelming, but that’s what some workers are nudged toward by their employers.