I'm writing something that explores the motivations behind calls for the construction of a U.S. - Mexico border wall and I've been looking into statistics regarding Mexico to U.S. immigration. I thought I would be able to say something like

Border security has become an increasingly important issue in modern politics as the increase in overall Mexican-born immigrant population in the U.S. places concern in the minds of many voters.

The only problem is that the number of Mexican-born immigrants in the US has actually decreased (albeit slightly) since 2010 [1] so I can't make that claim. Instead, I'd like to write

While the number of people apprehended attempting to cross the border illegally (used as an estimator for overall trends in illegal border crossings) has declined more than 1250% since 2000, border security seems to have become a dominating issue in post-millennium politics. [2]

However, I can't find evidence for this claim, and I don't expect it to be well studied/documented, but I do get the sense that it's true. However, that's a pretty awful way to back up a claim, so I'd at least like some anecdotal evidence to confirm my hunch.

Thanks!

edit: formatting