International infant mortality rankings: a look behind the numbers

Health Care Financing Review, Summer, 1992 by Korbin Liu, Marilyn Moon, Margaret Sulvetta, Juhi Chawla

Introduction

Rankings of infant mortality rates (IMRs) are among the most commonly cited international comparisons of health status. The very low ranking of the United States--19th among industrialized countries in 1989 (Table 1)--is often used to question the quality of health care in the United States. The U.S. rate of infant mortality (defined as the number of deaths among children under 1 year of age, divided by the number of births in a given year, and multiplied by 1,000) was more than 50 percent higher than those of Japan, Finland, and Sweden. These statistics have helped to spur interest in bringing down the number of infant deaths in the United States. Despite improvements--including a drop in the rate from 9.7 in 1989 to 8.9 in 1991--there is still a long way to go to bring U.S. rates in line with those of other countries.

Table 1
Infanti mortality rates in selected industrialized
                  countries: 1989
                          Infant
                         mortality
Rank   Country             rate
 1     Japan               4.4
 2     Finland             5.8
 3     Sweden              6.0
 4     Switzerland         6.8
 5     Netherlands         6.8
 6     Canada              7.1
 7     France              7.4
 8     West Germany        7.5
 9     Ireland             7.5
10     East Germany        7.6
11     Australia           7.7
12     Norway              7.8
13     Spain               7.8
14     Austria             8.3
15     Denmark             8.4
16     United Kingdom      8.5
17     Italy               8.6
18     Belgium             8.8
19     United States       9.7
20     Greece              9.8
21     Israel             10.0
22     New Zealand        10.2
23     Czechoslovakia     11.3
24     Portugal           12.2
25     Bulgaria           14.4
NOTE: The data were collected separately by East And West Germany.
SOURCE: Adapted from Wegman, 1991.

Infant mortality rates implicitly capture a complicated story, measuring much more than differences in health care across countries. For example, these rates are affected by the socioeconomic status of mothers and their children; we know that the age of the mother, birth weight of the child, quality of nutrition for the mother, and other factors are associated with mortality (Institute of Medicine, 1985; U.S. Congressional Budget Office, 1992; Hogue et al., 1987). Measurement differences in statistical reporting of vital events also figure into these comparisons. However, it would be a mistake to simply dismiss these measures. In assessing how the United States stacks up against other countries, these statistics offer opportunities to identify strategies for improving our health care system and to learn from other countries that have been more successful.

To expand our knowledge about the reasons behind international rankings, it is important to probe further. This article attempts some steps in that direction by taking a closer look at the statistics--sorting out real differences from artifacts of measurement, disaggregating the data where possible, and examining differences in risk factors across countries. Even industrialized countries differ substantially in approaches to treatment of health problems, use of resources, and presentation of data. Because of data limitations, we can only speculate on the impact of some of these differences and cite some of the important literature in the area. Much of the work in this area has focused on factors contributing to infant mortality in individual countries. This article summarizes some of the important research findings and attempts to put them in a broader framework. Our goal here is to offer a context for more informed debate on the meaning and interpretation of infant mortality statistics.

This survey of what we know about international comparisons is divided into several major areas. First, we examine measurement issues that can affect the rankings. We disaggregate infant mortality statistics into components such as neonatal and post-neonatal rates to provide more information about causes of international differences, and examine the occurrence of non-uniform reporting of vital events across countries. These differences can affect the relative ranking of the United States, but do not change the basic finding that we do less well with infant deaths than do many other industrialized countries. Second, we examine risk factors that affect infant mortality and try to trace how these factors differ internationally. Third, we turn to some simple simulations that help illustrate why infant mortality is so different in the United States as compared with other countries. The article concludes with a discussion of what these comparisons mean and what policy challenges await us in the attempt to reduce the rate of infant deaths in the United States.

Measurement issues

International comparisons are often criticized on measurement grounds. The IMR is a very crude measure, capturing both too much and too little. When all deaths up to 1 year of age are combined, some critics argue that the measure captures too many different problems and further disaggregation is appropriate. However, infant mortality statistics also leave out some vital information, such as ignoring fetal deaths before birth, that may distort the picture in another way. This debate over which of several measures to use illustrates the complexity of factors surrounding infant mortality.