Heterogeneity in Effects of ultrasound availability on male probability: OLS results
| By groups | Dependent variable: child is male | |||
|---|---|---|---|---|
| Maternal education | Household income | |||
| < Median (1) | ≥ Median (2) | < Median (3) | ≥ Median (4) | |
| First birth × ultrasound | −0.009 (0.009) | −0.007 (0.005) | −0.010* (0.006) | −0.007 (0.006) |
| Second birth × ultrasound | 0.024** (0.010) | 0.007 (0.005) | 0.014** (0.007) | 0.010 (0.007) |
| Third (or higher order) birth × ultrasound | 0.040*** (0.011) | 0.018** (0.008) | 0.021** (0.010) | 0.031*** (0.008) |
| Individual controls | Yes | Yes | Yes | Yes |
| County fixed effects | Yes | Yes | Yes | Yes |
| Year (of conception) fixed effects | Yes | Yes | Yes | Yes |
| County-specific linear time trends | Yes | Yes | Yes | Yes |
| Observations | 89,038 | 209,599 | 145,614 | 153,023 |
| R-squared | 0.0118 | 0.0064 | 0.0090 | 0.0073 |
Note: Individual controls include mother’s ethnicity, education, maternal age at conception and its squared term, gestation length and indicators for the timing of initial prenatal care visits. County fixed effects are separate indicator variables for each county. Year fixed effects are indicators that allow for unrestricted differences in year-to-year changes. Reported in parentheses are standard errors clustered by county.
↵* denotes statistical significance at the 10 percent level,
↵** at the 5 percent level,
↵*** at the 1 percent level.