A day after releasing second-quarter earnings, Columbus-based supplement insurance company Aflac saw its stock get hammered Thursday in trading on the New York Stock Exchange.At 3 p.m., the stock was trading at $53.18, down nearly 12 percent from Wednesday's close of $60.32. With an hour of trading left, the stock was down $7.12.Most of the market concerns deal with slowing policy sales in the U.S. and Japan.Investors were expecting a small increase in second-quarter Japan sales, but instead sales there declined by 4.9 percent. The company does 70 percent of its business in Japan. U.S. sales for the quarter were up 4.9 percent."I am surprised," said Aflac Senior Vice President for Investor Relations Ken Janke. "I personally think it was overdone. In the world of financial stocks, Aflac stocks are marked by an incredibly strong balance sheet, sound business model and strong growth model. The outlook on growth has not changed."