Looked into it some more. Mexican adults who are turned away at the border are not counted. Adults and children from other countries are put through removal proceedings, and that counts. Sometimes those proceedings take a few days to weeks, but it still counts. The point is that the policy of what counts and what doesn't had changed under Obama.

If it did change, I don't think that minor point disputes the deportation trend under Obama. What percentage of overseas immigrants take this risky (and expensive) route of arriving at a US border without a visa or some other immigration arrangements? Probably not a huge percentage. Vast majority of immigrants to US are still from Mexico so I doubt the numbers would be skewed significantly enough for it not to be comparable to previous presidents.

Here are some number showing ONLY interior removals: https://object.cato.org/sites/cato.org/files/wp-content/uplo...

But yes border removals also jumped as well.. Maybe there is already a wall there? Here is a breakdown of deportations by three categories (border, interior and unknown) https://object.cato.org/sites/cato.org/files/wp-content/uplo...

Certainly much of this is due to better tracking (dimishing of the unknown category), tighter enforcement, and more efficiency, but none of those arguments dispute the trend of higher deportations under Obama simply because it doesn't fit the overall narrative of Obama as a "compassionate" president.