Reporting from ground zero in the immigration debate, the Arizona Republic recently wrote that, “not every illegal immigrant in the United States snuck across the border. A very large number, perhaps as many as 5.5 million, entered legally with visas and then never left.”

As the article goes on to state, the 5.5 million figure (which would be nearly half of the nation’s estimated illegal immigrant population) is at best an educated guess. The U.S. Government hasn’t published nonimmigrant overstay rates since 1992. However, DHS’s picture of overstay rates has come into greater focus over the past several years as the systems and processes used to capture automated records of nonimmigrant arrivals and departures have improved significantly. As a result, we can say with much more certainty that the vast majority of these “overstayers” did not enter the United States under the Visa Waiver Program (VWP).

Current data shows a cumulative overstay rate from VWP countries of less than 1 percent. What’s more, this rate is likely overstated. For example, it includes travelers for whom DHS has no record of departure. While some of them may have overstayed, others likely departed without filling out the departure forms or using documents that can be easily matched to their incoming records. Also, all matching errors within the system are treated as overstays, which artificially increases the overstay rate.

While there are still data gaps – most notably, there is minimal collection of departure records at land ports and resource and logistical issues make it highly unlikely that DHS will have the additional capability to collect these records in the near future – the VWP data strongly suggest that the program has not been a substantial contributor to illegal immigration to the United States.