About 640 million people worldwide want to emigrate, and almost one-quarter of them would prefer to move to the United States, a poll released Friday indicated. The Gallup Organization said its survey of adults in 151 countries found about 13 percent of them would like to be living somewhere else. About 150 million people, based on the polling, would like to emigrate to the United States, followed by 45 million who would choose Britain, 42 million Canada, 32 million France and 31 million Saudi Arabia. In Liberia, 37 percent of would-be emigrants surveyed said they would prefer the United States, followed by 30 percent in Sierra Leone, 26 percent in the Dominican Republic, 24 percent in Haiti and 22 percent in Cambodia. The reasons people gave for wanting to emigrate include reuniting with family members, having the opportunity to start a business or to have more economic opportunity, and being able to talk freely. Gallup interviewed 452,199 adults 15 or older between 2009 and 2011 in 151 countries that are home to 97 percent of the global population. Interviewing was done either by telephone or face to face. The margin of error for the entire sample is about 1 percentage point with larger margins of error for individual countries.