First-Stage Estimates
| Firstborn Females | Firstborn Males | |||
|---|---|---|---|---|
| (1) | (2) | (3) | (4) | |
| Panel 1: Dependent Variable = Morethan2 | 0.59 | 0.59 | 0.45 | 0.45 |
| A next brother (D) | −0.219 (0.001)* | −0.221 (0.001)* | −0.063 (0.001)* | −0.064 (0.001)* |
| Twin2nd | 0.436 (0.004)* | 0.322 (0.005)* | 0.572 (0.003)* | 0.539 (0.005)* |
| Twin2nd × A next brother (D) | 0.223 (0.007)* | 0.067 (0.007)* | ||
| F-statistics for twins effect | 11,973 | 8,680 | 26,123 | 14,081 |
| Multivariate first-stage F-statistic | 2,046 | 5,892 | ||
| Panel 2: Dependent Variable = Morethan2 × A next brother (D) | ||||
| A next brother (D) | 0.480 (0.001)* | 0.476 (0.001)* | 0.419 (0.001)* | 0.416 (0.001)* |
| Twin2nd | 0.278 (0.005)* | 0.011 (0.003)* | 0.305 (0.006)* | 0.010 (0.002)* |
| Twin2nd × A next brother (D) | 0.526 (0.004)* | 0.586 (0.003)* | ||
| F-statistics for twins effect | 2,875 | 19,251 | 2,797 | 27,981 |
| Multivariate first-stage F-statistic | 5,110 | 12,866 | ||
| Panel 3: Dependent Variable = Sibsize | 2.80 | 2.80 | 2.55 | 2.55 |
| A next brother (D) | −0.428 (0.002)* | −0.428 (0.002)* | −0.100 (0.002)* | −0.101 (0.002)* |
| Twin2nd | 0.622 (0.012)* | 0.616 (0.019)* | 0.720 (0.010)* | 0.711 (0.014)* |
| Twin2nd × A next brother (D) | 0.012 (0.024) | 0.018 (0.020) | ||
| F-statistics for twins effect | 2,817 | 1,568 | 5,258 | 2,649 |
| Multivariate first-stage F-statistic | 488 | 1,191 | ||
| Panel 4: Dependent Variable = Sibsize × A next brother (D) | ||||
| A next brother (D) | 2.596 (0.002)* | 2.592 (0.002)* | 2.498 (0.001)* | 2.493 (0.001)* |
| Twin2nd | 0.317 (0.008)* | 0.015 (0.004)* | 367.000 (0.010)* | 0.013 (0.003)* |
| Twin2nd × A next brother (D) | 0.593 (0.013)* | 0.701 (0.014)* | ||
| F-statistics for twins effect | 1,372 | 1,203 | 1,489 | 1,474 |
| Multivariate first-stage F-statistic | 3,472 | 6,300 | ||
Notes: Panels 1 and 3 of this table report the first-stage estimates for fertility choice, using twinning at the second birth (Twin2nd) as instrument. Panels 2 and 4 report the first-stage estimates for the interaction between a next brother D and fertility choice, using D × Twin2nd as instrument. An interaction term for D × Twin2nd is included in Columns 2 and 4 when the interaction between D and fertility choice is included in the outcome equation. We include 416,315 firstborn females and 434,729 first born males born between 1978 and 1984 who have at least one sibling. Additional covariates include the full set of indicators for urban, the subject’s age and district of birth, parents’ education and years of birth, and mother’s age at the first birth. The multivariate first-stage F-statistics are constructed as described in Angrist and Pischke (2009, p. 217–218). Means of the fertility choice variable are in italics, and robust standard errors are in parentheses.