A common argument made against regulating small dollar credit products like payday loans is that regulation does nothing to address demand for credit, so consumers will simply substitute their consumption from payday loans to other products: overdraft, title loans, refund anticipation loans, pawn shops, etc. The substitution hypothesis is taken as a matter of faith, but there's surprisingly little evidence one way or the other about it (the Slips' own Angie Littwin has an nice contribution to the literature).
The substitution hypothesis is prominently featured in a New York Times piece that is rather dour about the CFPB"s proposed payday rulemaking. Curiously, the article omits any mention of the evidence that the CFPB itself has adduced about the substitution hypothesis. The CFPB examined consumer behavior after banks ceased their "deposit advance programs" (basically bank payday lending) in response to regulatory guidance. There's a lot of data in the report, but the bottom line is that it finds little evidence of substitution from DAPs to overdraft, to payday, or even to bouncing checks. The one thing the CFPB data examine is substitution to pawn shop lending. A recent paper by Neil Bhutta et al. finds evidence of substitution to pawn lending, but not to other types of lending, when payday loans are banned. I'd suggest that we're more likely to see a different substitution: from short-term payday loans (45 days or less) to longer-term installment loans. That's not necessarily a bad thing...if the regulations are well-crafted to ensure that lenders aren't able to effectively recreate short-term payday loans through clever structuring of installment loans. For example, a lender could offer a 56-day loan with four bi-weekly installment payments, but with a "deferral fee" or "late fee" offered for deferring the first three bi-weekly payments. That's the same as four 14-day loans that rollover, and the "late fee" wouldn't be included in the APR. That's perhaps an even better structure for payday lenders than they currently have.) The bigger point here is this: even if we think that there will be substitution, not all substitution is the same, and to the extent that the substitution is to more consumer-friendly forms of credit, that's good.