The companies leading the gig economy, and their boosters, have touted its potential to replace or substitute for regular, full-time jobs. But whether the gig is driving for Uber or delivering burritos for Postmates or walking dogs for Wag, such work isn’t actually replacing regular employment for those who do it, according to a new study from the JP Morgan Chase Institute. What’s worse: Earnings from such activities has plunged over the last five years, even as more people started participating in them, the study found.