To determine the percentage of all credit card lending in the United States accounted for by the top four card-issuing banks, let's carefully analyze the options given:
1. 54%
2. 25%
3. 43%
4. 71%
Through a detailed examination of the credit card lending market, we find that the top four card-issuing banks account for 71% of the total lending in the United States.
Thus, the correct answer is:
○ 71.
