While building a wall along the U.S. southern border, as well as hiring more Border Patrol agents, would help significantly in solving the problem of illegal immigration, another often less focused aspect of the problem has seen an increase. The Department of Homeland Security recently released its “Entry/Exit Overstay Report,” which estimates that as much as 40% of all illegal immigration is due to overstayed visas. This isn’t a new problem.

In fiscal year 2016, some 628,799 individuals overstayed their visas. Of that total, 544,676 are believed to still be in the country. These are individuals who lawfully entered the U.S. but remained beyond their allotted time and for whom no record of departure exists. Unfortunately, the percentage of overstays has seen recent increases — in 2015, it was 0.9%; in 2016, it increased to 1.07%. The greatest offenders tend to be students and exchange visitors whose visa overstays are 5.48%.

Homeland Security has been heavily invested in developing better biometric and biographic technology screening for those seeking entry, while focusing on tracking down visa overstay offenders has been less of a priority. Clearly, more Immigration and Customs Enforcement agents are needed to track down these growing numbers of visa overstays.

While most illegal aliens do not engage in violent criminal behavior, it’s a good reminder to note that two of the 9/11 hijacker terrorists overstayed visas. And while visitors to the U.S. are very much welcome, the laws are designed to protect citizen and visitor alike from those who would seek to exploit our nation’s good will for their own nefarious purposes.