The United Nations Office of Drugs and Crime, which has an office in New York City, estimated Colombia's coca crop at 155,000 acres in 2010, down from 182,500 acres in 2009 -- a 15 percent drop, the Los Angeles Times reported Friday.
Officials said the drop in Colombia is a result of the country's decade-long fight against drug trafficking. Colombia's drug-fighting effort is partially paid for by billions of dollars in U.S. aid.
The U.S. cocaine market has had "massive declines" in recent years, the report said, but it is still the world's largest market, with the sale of 157 tons of cocaine in 2009 for $37 billion. Sales in Europe were estimated at $36 billion.
Colombian officials said they couldn't rest on their laurels.
"We're doing very well, but we can't lower our guard," Colombian Interior Minister German Vargas Lleras said at a recent news conference.
Peru has had an opposite trend. Peru's crop increased for a third straight year, to 153,000 acres, making it second to Colombia in growing coca.