In 2011, Berkshire put $9 billion of cash to work buying Lubrizol, a maker of chemicals for automotive engines and a similar amount to take a 5.51% stake in IBM ( IBM). Those two 2011 investments typify Berkshire's strategy as it weeds out crisis-era investments and refocuses on long-term growth in earnings and dividends. Companies wholly earned by Berkshire added more than $9 billion in pretax 2011 earnings, contrasting with the $393 million that its only owned company MidAmerican energy contributed to earnings just seven years ago. Berkshire's purchases of Lubrizol and railroad Burlington Northern Santa Fe -- along with earlier acquisitions of Iscar, Marmon Group and MidAmerican -- set the fund up for consistent earnings growth in years to come, he said in his letter. "Unless the economy weakens in 2012, each of our fabulous five should again set a record, with aggregate earnings comfortably topping $10 billion," wrote Buffett. Those investments also help Berkshire to put its prolific cash to work in a manner that may help it outperform stock indices. In 2011, Berkshire's operating companies spent $8.2 billion for property, plant and equipment, eclipsing a previous record by more than $2 billion. For the U.S. economy, Buffett made a point that investing in those operating companies will be a minor stimulus that shows "invest in the U.S." is still alive and well. "About 95% of these outlays were made in the U.S., a fact that may surprise those who believe our country lacks investment opportunities," said Buffett in his letter. Berkshire's acquisitiveness may accelerate, based on the tone of Buffett's annual letter. The company is looking to make additional large purchases in an expected earnings boost. "We now have eight subsidiaries that would each be included in the Fortune 500 were they stand-alone companies," Buffett said. "That leaves only 492 to go. My task is clear, and I'm on the prowl." The second piece of Buffett's 2011 strategy was to take multibillion-dollar stakes in IBM and Bank of America ( BAC), in a move that Berkshire expects will add to its outperformance as earnings growth at those companies leads to increasing dividend payouts. With a $5 billion preferred stake and 700 million in-the-money warrant contracts in Bank of America, along with a $10.9 billion purchase of IBM shares, Berkshire now has four key investments that it expects will drive investment gains. Berkshire's largest investment is in Coca Cola ( KO), and its third largest-investment is in Wells Fargo ( WFC), with 8.8% and 7.28% share stakes, respectively. "Had we owned our present positions throughout last year, our dividends from the 'Big Four' would have been $862 million," said Buffett.