Meeting Homeland Security Sec. Janet Napolitano re: immigration

Comprehensive immigration reform was a topic at the March 2013 National League of Cities conference.  During Q & A with Secretary Napolitano, Plantamura noted that 40% of undocumented persons already in the U.S. are people who have overstayed the time limit on their visas.   Plantamura's questions:  Doesn't this near to half number demonstrate a need for an overhaul of the immigration system?  Wouldn't the wall between the U.S. and Mexico actually disallow people from leaving?

Photo published in Seminole Beacon, April 18, 2013