Recent survey results show that HMO enrollment is continuing its rapid advance. As of July 1, 1996, it accounted for 24.0 percent of the nation's population. While just two years earlier only three states had HMO enrollment totals of more than 30 percent of their populations (Massachusetts, 36.2 percent; California, 35.3 percent, and Oregon, 33.6 percent), by mid-1996 three states' percentages had exceeded 40 (Maryland, 47.1 percent; Oregon, 45.6 percent, and California, 42.6 percent), and six other states (including Massachusetts at 39.3) registered percentages in the thirties. The maps below show how the states were distributed in three major categories of HMO enrollment penetration in 1994 and 1996.