Immigration to the United States has continued to accelerate despite a slumping economy, a research group said in a report released Tuesday. A record 34 million legal and illegal immigrants live in the United States, nearly one-third of them from Mexico, according to the Center for Immigration Studies, a conservative think tank in Washington. About 4.3 million immigrants have entered the country since 2000, when the economy grew slowly. Roughly the same number arrived between 1996 and 2000, during a period of economic expansion. Illegal immigration accounted for nearly half the 4.3 million increase. About 9 million illegal immigrants live...