Sticky interest rates on credit card plans have long been a mystery. O
ne possible explanation is that banks maintain high rates because cons
umers' demand for credit card loans is inelastic. This study tests and
rejects that hypothesis. Demand for credit card loans is found to be
elastic with respect to interest rates charged, and the amount of deli
nquent loans is found to increase significantly more than total credit
card loans when interest rates drop. The results show that banks face
an adverse selection problem: Lowering the annual percentage rate of
interest (APR) would attract risky customers and increase delinquent l
oans at a significantly higher rate than loans in general. This induce
s banks to maintain high interest rates. The adverse selection hypothe
sis is further supported by the finding that banks' income from credit
card fees and interest increases with APR. Consumers' demand is also
found to be responsive to some of the enhancements added to the terms
of credit card plans. Banks may find it optimal to charge high interes
t rates, while adding enhancements in order to attract customers and r
aise their income at a low cost.