Demographic characteristics of ECLS-B children and mothers from the 9-month wave in the ECLS-Birth Cohort 2001–20021.

NA: Not applicable, for cells where the zero percent of the population fell into that category.(1) Percentages and Taylor series linearized standard errors are based on sample weighted data.(2) The sample size included in this table (N≈4600) includes all observations with complete covariates and included in the regression model at the 9-month visit. This differs from the total sample included in the regression analysis (N≈5000) since observations from children were included at every wave in which they had complete information on covariates. Approximately 400 children do not have complete data at 9-months, but do have complete data for at least one other time point.(3) We created a 5-category race/ethnicity variable (American Indian/Alaska Native, African American, Hispanic, Asian, white) from the mothers' report of child's race/ethnicity, which originally came 25 race/ethnic categories. To have adequate sample size in race/ethnic categories, we assigned a single race/ethnic category for children reporting more than one race, using an ordered, stepwise approach similar to previously published work using ECLS-B (3).