Between 1990 and 1991, provisional data show that the infant mortality rate decreased again, from 9.1 to 8.9, a decline of 2% in contrast to the 7% decline from 1989 to 1990. Birth, death, and marriage rates were also lower, but the divorce rate stayed at about the same level as in 1990. Natural increase in the population, excess of births over deaths, was less than 2 million, 4% less than the increase in 1990.
Detailed analysis of changes and of the influence of factors like age and race requires final data; at the time of preparation of this report final birth and death data were available only through 1989. For a variety of reasons, including staff shortages and delays in receipt of state data by the National Center for Health Statistics (NCHS), final data for 1990, which would usually have been available in late August 1992, are not expected before early 1993.
Unlike recent years, the decline in the infant mortality rate was only in the neonatal component, which decreased 3.6%. Postneonatal mortality increased, for the first time in many years, by 1.6%, suggesting that the decline in the total is related more to therapeutic advances in neonatology than to improved prevention.
Internationally, newly independent Latvia was added to the list of countries with rates less than 15, but Costa Rica was deleted. With the reunification of Germany the list shrank to 28 and, by default, the United States moved up from 21st to 20th.
Some 12.5 million births, less than 9% of the world total, took place in countries with under-5 mortality rates of less than 20 per 1000. At the other end of the scale, 42% of the world's births occurred in countries with under-5 mortality rates of more than 140 per 1000. The median under-5 mortality rate for those countries in 1990 was 189 per 1000, meaning that almost 20% of the infants born alive in these countries died before their fifth birthday.