Illinois' population losses are frequently cited in debates over the state's tax rates and business laws.
Last year, Census figures show Illinois was tied for the greatest rate of people leaving the state.
But Sarah Crane, with Moody's Analytics, says a federal immigration crackdown could make it even worse.
"Any reduction in trade or immigration will harm Illinois. ... The state is very reliant on immigration to even maintain its population."
Last year, a net of 83-thousand people left Illinois. If international immigration had been blocked completely - the state's population loss would have jumped by more than a third.
Illinois is among the top 10 states for people coming to America.
