the birth of their child (Smith, 2001).1 Changes in breastfeeding rates for low-income groups have historically lagged behind those of higher income groups (see U.S. Department of Agriculture, 1992, for a summary of historical breastfeeding practices), and we do not know whether breastfeeding rates among low-income groups have increased over recent years as much as rates in the total population have. Results from the Ross Laboratories Mothers Survey should be corroborated with data from other sources, which do not provide trends in breastfeeding but do give point-in-time estimates that are fairly recent, such as the National Health and Nutrition Examination Survey (NHANES III), the National Survey of Family Growth, the Continuing Survey of Food Intakes by Individuals, the Early Childhood Longitudinal Study Birth Cohort 2000, and the Infant Feeding Practice Survey. These datasets also include measures of family income, which the Ross Laboratories Mothers Survey data do not include. The panel has not reviewed the methods and assumptions used in the FNS life table estimates of the probability of breastfeeding over time. In our further review, we will consider these.
Sampling variability and random errors in reporting of income can create uncertainty in the estimates apart from the systematic biases that have been examined in this report. In the second phase of the study, the panel will investigate the appropriate level of confidence to place in the estimates by examining standard errors of the estimates of eligibility.