new york donald trump vow round deport america undocumented immigrants elect president could shrink economy around percent accord study release thursday conservative think tank american action forum research add concern republican presidential nominee policy proposals range tear international trade agreements build wall along u.s. border mexico 6.8 million 11 million immigrants live unite state illegally employ accord government statistics remove would cause slump 381.5 billion 623.2 billion private sector output washington-based non-profit say analysis study add remove workers could leave potentially millions job unfilled due lack legal workers will industries high share undocumented workers include farm construction hospitality accord research things donald trump say utterly unworkable say douglas holtz-eakin forum president top economic adviser senator john mccain 2008 presidential campaign ask study thursday trump say think analysts misunderstand immigration policy add want people come country come system saw report even right trump say interview cnbc certainly want shrink economy trump effectively lock republican nomination week call deportation anyone live unite state illegally argue foreign workers hold salaries contribute unemployment position draw strong opposition business leaders like conservative billionaire koch brothers well human right advocate trump anger opponents say mexico send rapists drug dealers unite state call temporary ban muslims enter country shore national security hard-line stance immigration also trigger strong support among many u.s. voters 52.6 percent respondents reuters/ipsos poll conduct september say want see undocumented immigrants deport compare 34.6 percent want see stay american action forum analysis use data bureau labor statistics estimate value output undocumented immigrants study factor potential impact mass deportations consumption investment economic factor group say u.s. economy project produce 18.7 trillion worth goods service 2016 accord international monetary fund loss 400 billion output would amount percent figure trump 's deportation plan could slice percent u.s. gdp study