Wal-Mart, the world\'s top retailer, said Tuesday its fiscal fourth-quarter earnings fell 15 percent as it cut prices in the United States amid fierce competition for consumer dollars. Wal-Mart posted $5.1 billion in net income for the three months ending January 31, compared with $6.1 billion in the year-ago period. Revenue rose 5.9 percent in the quarter to $123.2 billion, boosted in part by $2.4 billion from newly-acquired Netto stores in Britain and Massmart in South Africa. But it also took a $1.0 billion hit from unfavorable currency exchange rates. Earnings excluding special items were $1.44 per share, missing the average analyst forecast of $1.46. For the 2012 fiscal year, the Bentonville, Arkansas-based company reported earnings fell 4.2 percent from the prior year to $15.7 billion. Earnings per share for the year were $4.49, in line with market expectations. Full-year revenue rose 6.0 percent to $447 billion. \"We are pleased with Walmart\'s earnings performance for both the fourth quarter and the full year,\" Mike Duke, Wal-Mart Stores, Inc. president and chief executive, said in a statement. \"Today, every segment of our business is stronger than it was a year ago, and we\'re in a great position for fiscal year 2013.\" The discount giant estimated earnings per share in the current quarter between $1.01-1.06. In the United States, comparable store sales, sales at stores open at least a year, rose 1.5 percent in the fourth quarter, the second consecutive quarter of gains. \"Our price leadership is making a difference across the United States, as many families are settling into a new normal. Core customers remain cautious about their finances,\" Duke said. Bill Simon, Walmart US president and CEO, said the firm \"invested in price in the fourth quarter and will continue to do so through this fiscal year, so we can pass savings on to customers.\" With the US economy staging a fragile recovery from recession and unemployment remaining persistently high, Wal-Mart has faced rising competition from growing chains of so-called discount dollar stores, such as Family Dollar and Dollar Tree, and online retailers. Investors punished the company, a member of the blue-chip Dow Jones Industrial Average. Its stock plunged 4.2 percent to $59.81 in opening trade in New York.