The data source is the universe of birth certificates in Pennsylvania (2004–2013) matched to the Pennsylvania DEP Internal Operator Well Inventory. Maternal and infant demographic indicators and health outcomes are recorded at the time of birth. “Near, 0–1 km” indicates that the mother lives within 0 to 1 km of at least one well site. “Far, 3–15 km” indicates that the mother lives 3 to 15 km from the nearest well site. Columns (5) to (7) report P values from t tests of equality of means across the different samples indicated. Column (7) tests whether (2) − (1) = (4) − (3). This quantity is referred to as the difference-in-differences, or D-in-D.
Near, 0–1 km | Far, 3–15 km | P values | |||||
Before | After | Before | After | (5) | (6) | (7) | |
(1) | (2) | (3) | (4) | (1) − (2) | (3) − (4) | D-in-D | |
Mother characteristics | |||||||
Married | 0.68 | 0.61 | 0.62 | 0.63 | 0.00 | 0.00 | 0.00 |
Black | 0.01 | 0.02 | 0.12 | 0.06 | 0.01 | 0.00 | 0.00 |
Hispanic | 0.01 | 0.01 | 0.02 | 0.02 | 0.66 | 0.00 | 0.57 |
<High school | 0.11 | 0.12 | 0.11 | 0.10 | 0.27 | 0.00 | 0.01 |
High school | 0.28 | 0.31 | 0.26 | 0.25 | 0.02 | 0.00 | 0.00 |
Some college | 0.32 | 0.32 | 0.28 | 0.29 | 0.89 | 0.00 | 0.43 |
College | 0.22 | 0.17 | 0.22 | 0.23 | 0.00 | 0.00 | 0.00 |
Advanced | 0.08 | 0.08 | 0.13 | 0.13 | 0.74 | 0.69 | 0.74 |
<20 years old | 0.06 | 0.06 | 0.06 | 0.05 | 0.89 | 0.00 | 0.11 |
20–24 years old | 0.21 | 0.26 | 0.22 | 0.21 | 0.00 | 0.00 | 0.00 |
25–29 years old | 0.30 | 0.31 | 0.29 | 0.29 | 0.42 | 0.00 | 0.86 |
30–34 years old | 0.26 | 0.23 | 0.27 | 0.28 | 0.01 | 0.00 | 0.00 |
>35 years old | 0.17 | 0.14 | 0.17 | 0.16 | 0.01 | 0.00 | 0.07 |
Infant characteristics | |||||||
Male | 0.50 | 0.52 | 0.51 | 0.52 | 0.24 | 0.27 | 0.32 |
First born | 0.42 | 0.41 | 0.43 | 0.43 | 0.66 | 0.15 | 0.84 |
Second born | 0.33 | 0.34 | 0.33 | 0.33 | 0.46 | 0.05 | 0.68 |
Third born | 0.16 | 0.16 | 0.15 | 0.15 | 0.79 | 0.64 | 0.73 |
Fourth and up | 0.09 | 0.09 | 0.09 | 0.09 | 0.90 | 0.51 | 0.98 |
Health outcomes | |||||||
Low birth weight | 0.05 | 0.07 | 0.06 | 0.06 | 0.04 | 0.00 | 0.01 |
Birth weight | 3354.35 | 3312.81 | 3316.94 | 3331.08 | 0.01 | 0.00 | 0.00 |
Health index | 0.05 | 0.01 | 0.01 | 0.02 | 0.01 | 0.00 | 0.00 |
n | 4871 | 1798 | 133,107 | 78,366 |