As Donald Trump touts increasingly aggressive plans to crack down on illegal immigration, economists are wary that his proposals would deal a massive blow to the U.S. job market, which has stayed strong thanks in part to foreign-born workers.

Trump has made strict immigration restrictions — including mass deportations, detention camps and an expanded border wall — core to his promise of a stronger U.S. economy, arguing that immigrant workers reduce wages for everyone and take jobs from native-born Americans. Those proposals lack specificity and detail, so it’s difficult to know exactly how he would carry out his plans.