from The Economist shows that the number of unauthorized immigrants in the USA increased from 1990 to the start of the Great Recession, and that in the last years of the Bush administration, some of those illegals went home. The Obama administration has kept the number relatively constant, in spite of the economic recovery.
The recent executive order, quoting the Council of Economic Advisers via The Economist:
will boost GDP in the next decade by between 0.4% and 0.9%, mostly because of provisions unrelated to illegal immigration. These give foreign entrepreneurs more ways to get into America, allow the spouses of skilled visa-holders to work, and let foreign-born science graduates spend more time in America doing their training.More needs to be done. The bill passed by the Senate last year but blocked by the House Republican leadership would be a good start.