Since the 1970's there has been growing evidence supporting the frequently heard conjecture that credit cards encourage spending. For example, it is known that people who own more credit cards make larger purchases per department store visit (Hirschman 1979), and that restaurant tips are larger when payment is by card (Feinberg 1986). There is also evidence that credit card users are more likely to underestimate or forget the amount spent on recent purchases (Soman 1999). Perhaps the most compelling evidence, however, is that offered in an experimental analysis of the effect by Feinberg (1986). In that investigation participants were asked how much they would be willing to.
