Table 9.

Lead and Reading Test Scores—Robustness

	Drop obs. with imputed natality (1)	Include address FE (2)	Impute all pre-school lead (3)	Weight earlier exposure more (4)
Panel A. Ordinary least squares
Single random draw of blood lead levels	−0.295 [0.0252]	−0.262 [0.0657]
Geometric mean of lead (imputed)			−0.296 [0.0230]
Geometric mean of lead (weighted)				−0.320 [0.0345]
Observations	59,877	26,131	70,678	70,678
R2	0.224	0.640	0.223	0.221
Fixed effect	Tract	Address	Tract	Tract
Number of fixed effects	233	10,157	233	233
Panel B. IV with first random draw as dependent variable and average of other draws as instrument
Single random draw of blood lead levels	−0.373 [0.0328]	−0.340 [0.0791]
Observations	47,603	20,521
Fixed effect	Tract	Address
Number of fixed effects	233	10,157
Panel C. IV with geometric mean of lead as dependent variable and predicted certificate as instrument
Geometric mean of lead	−0.600 [0.415]	−1.390 [0.643]
Geometric mean of lead (imputed)			−1.097 [0.390]
Geometric mean of lead (weighted)				−2.470 [0.898]
Observations	59,877	26,131	70,678	70,678
R2	0.224	0.640
Fixed effect	Tract	Address	Tract	Tract
Number of fixed effects	233	11,298	233	233

Notes: Standard errors clustered at the tract level are shown in brackets. Fifteen percent of the children in our sample were not born in Rhode Island and therefore there is no natality data available for them. They are dropped in column 1. Column 2 shows estimates for the sample of addresses with more than one child and including address fixed effects. Column 3 uses an alternative measure of lead exposure: we impute lead levels for months with no lead test based on an average of the two nearest months with measured lead levels. Column 4 shows estimates based on an imputed lead measure where we give greater weight to measures taken at younger ages (see text for more detail on imputation and weighting methods).