Mass deportations would likely have a significant and negative, effect on the US economy because these migrants are working in a very wide range of jobs, and many of them jobs that Americans seem reluctant to do.
I could talk for hours about why American workers don’t take these jobs. It’s a very complicated problem, and it was very visible during the last election. There are many long-term unemployed or semi-employed white men in rural regions who have remained in place rather than migrating to regions of economic expansion, where migrants are found in larger numbers. Rates of geographical mobility have actually declined in the United States over the past two decades. These under- and unemployed white men demanded during the election that Trump bring back their jobs. It’s almost became a slogan: bring our jobs back, bring the work in the coal mines back to us.
Unlike migrants, many men have not been willing to move to where economic opportunities exist.
Unlike migrants, many men have not been willing to move to where economic opportunities exist. Neither have many been willing to take the jobs that do exist or expand in such areas – they do not regard working in fast food sites as a job they can do. Those are jobs taken by women, minorities, and younger workers. Many white men in economically declining areas won’t even retrain for jobs in expanding arenas such as healthcare – nursing at any level is still regarded as appropriate only for women in many men’s eyes.
Rural areas of economic decline are very complicated places but their problems are not likely to be solved by the deportation of eight million undocumented workers since jobs of the undocumented are located elsewhere, mainly on the coasts and in more urban areas. So deportation is likely mainly to increase automation and drive up consumer prices.
Historically there have been cases where Americans took jobs formerly done by migrants. In the 1930s, California deported several hundred thousand Mexicans – some of them went voluntarily, some of them were literally put on trains, with their citizen children. At that time there was a very large migration of white, rural Americans, from Arkansas and Oklahoma, to California. These were farmers who were losing their farms because of the 1930s drought and because a long-term crisis in agricultural prices had left them with no income to make mortgage payments on the lands they farmed.
You should remember, though, that the internal migration to California in the 1930s took place in the absence of even the most rudimentary welfare state provisions, provisions that do now exist in the USA. In today’s West Virginia, many of the men who support Trump are able to survive because of this rudimentary American welfare state. Some of them are on long term disability, and of course now live in an economy where women in their families are often wage earners, perhaps not earning much but nevertheless allowing families to survive and life to continue without moving away.