The third chapter of the dissertation, ' Optimal Payment Cards Fees: A Credit-
Debit Comparison', discusses how policy can solve adverse effects created by packaging.
The paper compares optimal interchange fees in credit cards versus debit cards.
Compared to debit cards, credit cards raise efficiency by allowing convenient borrowing,
but also tax nonholders in order to finance the rebates paid to credit card users.
A welfare enhancing and legally feasible policy is suggested, under which the regressive
tax is cancelled while the efficiencies of credit cards are preserved. An outcome
of the proposed policy is that credit cards are used for credit purposes only, while
debit cards are used as a convenient payment instrument.