4. Results
Estimates of the effects of pollution on all mothers within 10 km of a monitor are shown in Table 2.
Each group of 3 columns shows estimates of Eqs (1)–(3) for a different pollutant.
The mother fixed effects model, Eq. (3), is only identified from mothers with at least 2 children in the sample.
To assure that the differences between the models are not driven by changes in the sample composition, the sample for estimating all three equations is restricted to children with at least one sibling in the sample (corresponding to column
(5) of Table 1).
In all models we cluster standard errors at the census tract level to allow for common shocks to mother’s exposed to comparable levels of pollution.