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EXAMPLE

Simple Analysis of Birth Weight and Infant Mortality

Birth-weight distributions appear to be heterogeneous and composed of a primary subpopulation and a secondary subpopulation. These may be interpreted as the "normal" subpopulation and the "compromised" subpopulation. The secondary subpopulation accounts for the heavy upper and lower tails of the overall birth weight distribution. See Figure 1

The secondary subpopulation has lower infant mortality at every birth weight compared to the primary subpopulation. This may be attributed to selection due to differential fetal loss. See Figure 2.

Comparisons of African American and European American infant mortality indicate that primary mortality is higher among African American births, whereas secondary mortality is lower among African American births, probably because of heavier fetal loss among African Americans. See Figure 2.

The pediatric paradox is due to the significantly lower secondary mortality at the lower birth weights and the higher proportion of secondary births among African Americans. See Figure 3.

These results suggest that the health differential between African Americans and European Americans, are significantly underestimated using the standard methods. 

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