NEW YORK ( TheStreet) -- Over the course of the week, investors and market commentators have been mulling over the 13F regulatory filings released by individuals including George Soros, Steve Cohen, John Paulson, and Warren Buffett.These documents typically have provided plenty of interesting clues and insights into the current mindsets of these Wall Street notables. According to the filing, Buffett made only minor adjustments to his legendary investment portfolio during the opening quarter of 2011. The most noticeable change was the addition of Mastercard ( MA). As of the end of March, Buffett's stake in the credit card company totaled 216,000 shares. Aside from this new position, the investor also trimmed his stake in ConocoPhillips ( COP). This is not the first time that Buffett has tapped into the credit card industry. On the contrary, American Express ( AXP) is a long-standing Berkshire Hathaway ( BRK.A) holding and is currently his third largest position, accounting for a more than 10% stake of the portfolio. As noted by many, the decision to gain exposure to Mastercard is not surprising. Rather, the move can likely be traced back to Buffett's newest hire, Todd Combs, a former hedge fund manager-turned-potential Buffett successor. Prior to joining Berkshire Hathaway, Comb's hedge fund, Castle Point, held a large stake in the credit card company as well. Buffett's attraction to credit card companies like Mastercard and American Express can be viewed another play on the strength of the U.S. consumer. Throughout the slow and often arduous economic recovery, he has consistently maintained a bullish outlook for the United States. >>View Warren Buffett's Portfolio Although financials represent the largest slice of Buffett's portfolio's sector breakdown, the Oracle of Omaha also boasts heavy exposure to companies that will be influenced by the consumer's resurgence. Top portfolio components include Coca-Cola ( KO), Procter & Gamble ( PG), Kraft Foods ( KFT) and WalMart ( WMT). Like Coca-Cola and WalMart, the long-term strength of Mastercard and American Express will heavily depend on the consumer's recovery. As individuals regain confidence, they will become increasingly willing to use credit cards in order to make big ticket purchases. As noted by Bloomberg following news of Buffett's actions, the consumer has already started off 2011 on a postive note. According to the quarterly report issued by the U.S. Commerce Department, retail sales during the first three months of 2011 jumped nearly 3%.