The healthcare sector is one of the largest and most complex in the U.S. economy, accounting for close to a fifth of overall gross domestic product (GDP), according to the OECD. Some of the highest-quality care in the world can be found in the U.S., but in terms of the population's overall health the U.S. lags other wealthy, developed countries. Life expectancy is 78.8 years, according to the OECD, below the club's average of 80.6 (the OECD's 35 members are mostly rich, industrialized countries in Europe and North America).