About 43,000 Americans are enrolled in degree programs outside the United States, with a plurality (44 percent) pursuing master's degrees, 39 percent seeking undergraduate diplomas, and 17 percent in doctoral programs, according to a study released Wednesday by the Institute for International Education. The report, a supplement to the institute's annual Open Doors report on the flow of students into and out of the United States, was done in conjunction with Project Atlas. The leading fields for degree study were the humanities, social sciences, and business and management, and Britain was the top destination.