Consolidation and the transformation of competition in health insurance.

This paper presents data on fifty state and substate insurance markets, in terms of the 2003 relative shares of the largest health plans and the antitrust index of concentration. It presents 2000-03 data on rates of growth in premiums, costs, operating earnings, returns on equity, and share prices for the nation's largest health plans (Well-Point, Anthem, Aetna, and CIGNA). Private insurers face renewed price and profit pressures in the short term, but long-term prospects depend on the emergence of new products and new competitors in an increasingly consolidated industry.