You may begin with:

• Statista provides quick statistics on the topic
• Nilson Report(It is in print in the current periodicals section of the Stamps Reading Room) Publishes statistics and in-depth articles on the credit card system and other payment methods. An index to issues is available online.
• The Federal Reserve collects statistics on Consumer Credit.

Additional resources: 

• IBIS World provides market reports on the topic. You may begin a search by using: "credit card" payment
• Bloomberg Academic type CCR and hit GO to display credit card reports from issuers.