NEW YORK — More than half of American smokers have tried to quit the habit as the daily use of cigarettes fell, U.S. health officials say.About 19 percent of U.S. adults, or 43.8 million, reported smoking daily or most days in 2011, little changed from 19.3 percent a year earlier, according to data from the U.S. Centers for Disease Control and Prevention on Thursday. That's down from more than 20 percent in 2005. About 52 percent of those surveyed reported trying to stop smoking in the preceding year.The number of cigarettes Americans are smoking each day has fallen. In 2011, 9.1 percent of daily smokers reported puffing on more than 30 cigarettes daily, a drop from 12.6 percent six year earlier. Even so, the number of smokers in the United States is still too high, exceeding the 12 percent goal for American adults, the CDC said."Tobacco use remains the single largest preventable cause of death and disease in the United States," the Atlanta-based agency said in its report, citing 2010 data from the Surgeon General showing that about 443,000 U.S. adults die from smoking-related causes annually.Smoking costs the United States an estimated $96 billion in direct medical expenses and $97 billion in lost productivity each year, according to the report. The CDC called for measures including raising the price of tobacco products, increasing access to programs intended to help people quit smoking, airing graphic commercials about the dangers of tobacco and implementing smoke-free laws."Such population-based interventions have been shown to reduce population smoking prevalence as well as overall smoking intensity," the CDC said.Those smoking fewer than 10 cigarettes a day increased to 22 percent in 2011 from 16.4 percent six years earlier, the agency said.