Has the potency of pot changed since President Obama was in high school?

Marijuana today is "genetically modified," with THC levels that "far surpass the marijuana" of the 1970s.    YES

The number of samples confiscated with a THC concentration greater than 9 percent has increased significantly, from 3.2 percent in 1993 to 21.5 percent of the 1,635 marijuana samples collected in 2007.