The tragic shooting at a movie theater in Aurora, Colo., on July 20 has reignited a long-running debate about gun control and laws allowing citizens to carry concealed weapons. Some argue that armed civilians in the movie theater could have mitigated Friday's massacre, whereas others believe that more guns could have led to even more confusion and greater loss of life.

In fact, more guns than ever are in citizens' hands today. Although a lower percentage of the U.S. adult population owns them, those who do own several; the average number of guns per owner is up from 4.1 per person in 1994 to 6.9 in 2004.

Growing roughly in tandem with rising gun ownership is the increase of more lenient regulations allowing people to carry concealed weapons. These laws are up markedly. Concealed-carry laws can be of the "shall issue" or "may issue" variety; in "shall issue" states, law enforcement must issue a permit if certain criteria are met, whereas in "may issue" states, law enforcement has discretion.  Colorado is a "shall issue" state, although some businesses, such as the movie theater where the shooting occurred, prohibit guns on their premises.

More states are also considering legislation that would permit the carrying of concealed weapons in bars, churches and on college campuses, despite recent tragedies. Both trends are worrisome because they place more hidden guns in more public places. Whether lenient gun-control laws contribute to an increase in gun violence is a hotly contested issue, but research to determine the root of such associations is necessary so that lawmakers can protect citizens' lives as well as their rights.

Graphic by Jen Christiansen