TABLE 1.

Sample means for all mothers and those potentially exposed

	All	Any contam.	Any chem.	Switchers Any contam.	Switchers Any chem.
No. of observations	521978	42256	35557	80507	68308
Low birth weight	0.0521	0.0578	0.0613	0.0578	0.0608
	(0.0003)	(0.0011)	(0.0013)	(0.0008)	(0.0009)
Preterm (<37 wks)	0.0739	0.0776	0.0811	0.0779	0.0802
	(0.0004)	(0.0013)	(0.0014)	(0.0009)	(0.0010)
Mom’s age
<19	0.0336	0.0461	0.0519	0.0530	0.0591
	(0.0002)	(0.0010)	(0.0012)	(0.0008)	(0.0009)
19–24	0.2029	0.2753	0.3017	0.2886	0.3144
	(0.0006)	(0.0022)	(0.0024)	(0.0016)	(0.0018)
25–34	0.5699	0.5256	0.5091	0.5186	0.5008
	(0.0007)	(0.0024)	(0.0027)	(0.0018)	(0.0019)
35+	0.1935	0.1530	0.1372	0.1398	0.1257
	(0.0005)	(0.0018)	(0.0018)	(0.0012)	(0.0013)
Mom’s race
African-American	0.1691	0.2235	0.2474	0.2242	0.2446
	(0.0005)	(0.0020)	(0.0023)	(0.0015)	(0.0016)
Hispanic	0.2317	0.3310	0.3589	0.2986	0.3223
	(0.0006)	(0.0023)	(0.0025)	(0.0016)	(0.0018)
Non-Hisp. white	0.5166	0.4011	0.3566	0.4306	0.3928
	(0.0007)	(0.0024)	(0.0025)	(0.0017)	(0.0019)
Mom’s education
No HS diploma	0.1521	0.2407	0.2685	0.2263	0.2498
	(0.0005)	(0.0021)	(0.0024)	(0.0015)	(0.0017)
HS	0.2780	0.2405	0.3302	0.314	0.3241
	(0.0006)	(0.0023)	(0.0025)	(0.0016)	(0.0018)
Some college	0.4228	0.3498	0.3237	0.3587	0.3374
	(0.0007)	(0.0023)	(0.0025)	(0.0017)	(0.0018)
College or adv.	0.1308	0.0806	0.0657	0.0835	0.0701
	(0.0005)	(0.0013)	(0.0013)	(0.0010)	(0.0010)
Mother smokes	0.0774	0.0917	0.0952	0.0885	0.0903
	(0.0004)	(0.0014)	(0.0016)	(0.0010)	(0.0011)
Mother is married	0.6950	0.5728	0.5311	0.5864	0.5511
	(0.0006)	(0.0024)	(0.0026)	− 0.0017	− 0.0019
Mother moved	0.3719	0.3369	0.3118	0.3854	0.3606
	(0.0007)	(0.0023)	(0.0025)	− 0.0017	− 0.0018

NOTES: Standard errors in parentheses. Switchers refer to siblings in families where one child was exposed and the other was not. ‘Mother moved’ is equal to one if the mother moved at least once between births.