The next two decades will see dramatic changes in the health needs of the world's populations. In the developing regions where four-fifths of the planet's people live, noncommunicable diseases such as depression and heart disease are fast replacing the traditional enemies, such as infectious diseases and malnutrition, as the leading causes of disability and premature death. By the year 2020, noncommunicable diseases are expected to account for seven out of every ten deaths in the developing regions, compared with less than half today. Injuries, both unintentional and intentional, are also growing in importance, and by 2020 could rival infectious diseases worldwide as a source of ill health. These changes are expected because of the rapid aging of the developing world's populations, As a population's birth rate falls, the number of adults relative to children increases, and the population's commonest health problems become those of adults rather than those of children. In China, some other parts of Asia and Latin America, this so-called" epidemiological transition" is already much further advanced than many public health specialists appreciate. In all regions the rapidity of change, and the very large absolute numbers involved, will pose serious challenges to health-care systems and force difficult decisions about the allocation of scarce resources. Yet, until now, many governments have lacked even the most basic data they needed to inform debate and to assess priorities for public health.

Now, for the first time, this gap has been filled with a landmark publication. Researchers at the Harvard School of Public Health and the World Health Organization, with more than 100 collaborators from around the world, have produced a comprehensive, internally consistent and comparable set of estimates of current patterns of mortality and disability from disease and injury for all regions of the world, with