Illegal immigration outcomes on the U.S. southern border

With respect to illegal immigration, those laws require preventing entry of those without lawful permission to enter. [...]the core strategic measure of border enforcement success is the number of unauthorized migrants who escape detection and successfully enter the United States illegally.2 I will refer to this measure as the number of successful illegal entries. If the border was perfectly open, then all entries would by definition be legal, and the probability of apprehension would be irrelevant, because there would be no border enforcement. Because these two states never actually apply in the real world, it makes more sense to estimate the values of the three core measures highlighted above and try to understand what they imply about the state of border security. [...]it must credibly report on border security outcomes and determine whether its actions have impacted those outcomes. [...]there are more political and institutional rewards in Washington for focusing on facilitation of cross-border travel and trade flows, which supports the economy and minimizes complaints from a traveling and trading public.