Retail sales unexpectedly rose in April, pointing to underlying strength in the economy and leading forecasters to bump up second-quarter growth estimates. The surprise gain in retail sales, which account for about 30 percent of consumer spending, was the latest sign of resilience in an economy that has been hit by belt-tightening in Washington as the government tries to cut its budget deficit. "It's more indication that our economy is growing. It's not growing as rapidly as a lot of people would like, but things are improving," said Tom Hall, an economics professor at Miami University's Farmer School of Business in Oxford, Ohio. Retail sales edged up 0.1 percent after a 0.5 percent drop in March as households bought automobiles, building materials and a range of other goods, the Commerce Department said on Monday. Economists had expected a decrease of 0.3 percent. So-called core sales, which strip out automobiles, gasoline and building materials and corr