information about what does and does not work to produce good outcomes in health care. Over the last 30 years, the increase in such trials has been staggering—from just over 100 to nearly 10,000 annually. The first 5 years of this 30-year period accounts for only 1 percent of all the articles in the medical literature, while the last 5 years accounts for almost half (49 percent) (Chassin, 1998), and there is no indication that this rate is slowing. Studies on the effectiveness of medical practice have also become increasingly sophisticated, involving complex issues of patient selection and statistical procedures.

As the knowledge base has expanded, so too has the number of drugs, medical devices, and other technological supports. For example, the average number of new drugs approved per year has doubled since the early 1980s, from 19 to 38 (The Henry J.Kaiser Family Foundation, 2000). Between 1990 and 1999, 311 new drugs were approved by the U.S. Food and Drug Administration (U.S. Food and Drug Administration, 2000). The cost of pharmaceuticals is the most rapidly growing component of health care expenditures. As clinical science continues to advance, the challenge of managing the use of existing and new pharmaceuticals and health technologies will intensify.

Without substantial changes in the ways health care is delivered, the problems resulting from the growing complexity of health care science and technologies are unlikely to abate; in fact, they will increase. For example, work being done in genomics offers significant promise for disease diagnosis and, eventually, treatment. Engineering advances in miniaturization will place diagnostic, monitoring, and treatment tools directly into the hands of patients as science improves and costs are reduced. And the application of epidemiological knowledge to large populations and databases will enable us to understand more and more about the dynamics of wellness and disease.

Increase in Chronic Conditions

One of the consequences of advances in medical science and technology is that people are now living longer. Although health care is by no means the only factor that affects morbidity and mortality, innovations in medical science and technology have contributed greatly to increases in life expectancy. The average American born today can expect to live more than 76 years (National Center for Health Statistics, 2000). Roughly 1 additional year has been added to life expectancy every 5 years since 1965.

Because of changing mortality patterns, those age 65 and over constitute an increasingly large number and proportion of the U.S. population. Today, this age group accounts for approximately 1 in 8 persons, or 13 percent of the population (National Center for Health Statistics, 1999). In 2030, when the large baby boom cohort has entered old age, 1 in 5 persons (20 percent) is expected to be in this age group. These demographic changes have important implications for the organization of the health care delivery system, but we have yet to address them in any

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