These statistics are hopelessly confounded by changes to the definition of "deportation" and are not to be viewed as reliable: https://www.washingtonpost.com/news/monkey-cage/wp/2014/04/2...
"CORRECTION: The original post claimed that Obama had de-emphasized removals and concentrated on returns and that the ratio of his removals to returns was skewed toward returns compared to his predecessors. That claim is not correct because based on DHS’s data, (Table 39: Aliens Removed and Returned, FY 1892-2012) his cumulative numbers since taking office show Obama has removed a total of 1,974,688 people and returned 1,609,055 others. There have been more returns than removals only in FY 2009 and 2010. Moreover, comparing across administrations is not wise given the changes in law and counting procedures."
So even if you count removals only, they removed ~2mn people and this article was published in 2014. If you add returned, this swells to nearly 4mn
Our immigration process is severely broken especially for migrant workers. They are an integral part of our economy and would, in most cases, choose to come here legally if they were given the opportunity. What we should be doing is giving these people work visas with a path to citizenship. We have already seen the adverse effects of eliminating illegal immigrants from being able to work as farm labor, crops rot in the field [2], and when prices rise, it will present opportunities to importers to put farmers out of business for good.
I should also state that I have no issues with deporting, though I don't understand why we don't incarcerate, unauthorized immigrants who commit violent crime(s). These people should be removed from our society.
[1] https://www.washingtonpost.com/blogs/plum-line/wp/2017/01/13...
[2] http://www.forbes.com/sites/realspin/2012/05/17/the-law-of-u...
I read the other day that this is an artifact of a change made under Bush that redefined deportation to include turning anyone away at the border.