Credit card giant Capital One agrees to buy rival Discover Financial, potentially creating one of the largest credit card companies by loan volume. Capital One market cap stands at $52 Billion while Discover’s market cap stands at $28 Billion. The new combined entity will be one of the largest in terms of credit card market share, one of the largest in terms of transaction volume, and also one of the largest in the US by number of cards in circulation, putting it in direct competition with Visa and Mastercard.