Twenty-four states and the District of Columbia have selected the health insurance plan in their state that will serve as the "essential health benefit" package sold by all insurers participating in the new insurance exchanges, or marketplaces, and in the individual and small-group markets, according to a Commonwealth Fund brief. Designed to improve the comprehensiveness of health coverage, the essential health benefit, which takes effect January 2014, covers 10 broad service categories, including ambulatory patient care, hospitalization, maternity and newborn care, and prescription drugs