Payday loans are small, short-term, unsecured loans. The typical borrower can not easily borrow elsewhere, and the interest rates on payday loans are quite high. These factors generate enormous criticism of payday lenders for "exploiting" borrowers.
Economists Susan Payne Carter and William Skimmyhorn of the United States Military Academy provide evidence on this criticism:
We evaluate the effect that payday loan access has on credit and labor market outcomes of individuals in the U.S. Army. ... We find few adverse effects of payday loan access on service members when using any of [our empirical] methods, even when we examine dozens of subsamples that explore potential differential treatment effects.
This should not be a surprise: for people with poor credit, payday loans can be better than the alternatives. These include going to a loan shark, which is even more expensive; or not borrowing, even to fund crucial medical care, or a rental payment that avoids eviction, or travel to secure a job.