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Fields Changed

Registration

Field Before After
Trial Start Date July 21, 2026 July 22, 2026
Last Published July 23, 2026 08:12 AM July 25, 2026 03:15 AM
Intervention Start Date July 21, 2026 July 22, 2026
Primary Outcomes (Explanation) Outcome 1: choice probability of the larger-family option, estimated via a linear probability model with respondent fixed effects (and via a scaled/heteroscedastic logit as the structural counterpart), on the reduced-form contrasts in money price (log income ratio) and time price (non-leisure hours). Outcome 2 -- the normal-good test: the registered output is the confidence interval on the income-interaction parameter (mu) from the reduced-form specification, not a reject/fail-to-reject verdict. Because the reduced-form model is a linear probability model, its coefficients measure changes in choice probability, not utility; we report mu, its confidence interval, and the implied change in the predicted probability of choosing the larger-family scenario across the displayed income range (p25 to p90), with a confidence interval obtained by propagating coefficient uncertainty. A tight interval bounding mu near zero is the substantive finding that the value of children is flat as a share of income (normal in dollars but not in share). The structural interaction is reported as a corroborating cross-check. Outcome 3 -- willingness to pay: reported in dollars and in leisure/sleep hours for one and for two additional children, by education stratum, from the structural model (which supplies the utility metric; WTP is not derived from the reduced-form probability coefficients). WTP for each child contrast is defined as the compensating change in income that equates utility between child levels under the full structural utility function, including the income interaction, holding time fixed; reported at each displayed income level with the p50 value as the headline within-stratum quantity. We also report the parity-zero, one-versus-none willingness to pay as the first-birth extensive- margin value. Confirmatory tests (hidden until unlock): H1, demand slopes down in the money price; H3, demand slopes down in the time price (both one-sided at 5%); H2, the income-interaction (normal-good) test, reported as the confidence interval on mu. H1-H3 are treated as three distinct hypotheses with no family-wise multiplicity correction. Outcome 1: choice probability of the larger-family option, estimated via a linear probability model with respondent fixed effects (and via a scaled/heteroscedastic logit as the structural counterpart), on the reduced-form contrasts in money price (log income ratio) and time price (non-leisure hours). Outcome 2 -- the normal-good test: the registered output is the confidence interval on the income-interaction parameter (mu) from the reduced-form specification, not a reject/fail-to-reject verdict. Because the reduced-form model is a linear probability model, its coefficients measure changes in choice probability, not utility; we report mu, its confidence interval, and the implied change in the predicted probability of choosing the larger-family scenario across the displayed income range (p25 to p90), with a confidence interval obtained by propagating coefficient uncertainty. A tight interval bounding mu near zero is the substantive finding that the value of children is flat as a share of income (normal in dollars but not in share). The structural interaction is reported as a corroborating cross-check. Outcome 3 -- willingness to pay: reported in dollars and in leisure/sleep hours for one and for two additional children, by education stratum, from the structural model (which supplies the utility metric; WTP is not derived from the reduced-form probability coefficients). WTP for each child contrast is defined as the compensating change in income that equates utility between child levels under the full structural utility function, including the income interaction, holding time fixed; reported at each displayed income level with the p50 value as the headline within-stratum quantity. We also report the parity-zero, one-versus-none willingness to pay as the first-birth extensive- margin value. Confirmatory tests: H1, demand slopes down in the money price; H3, demand slopes down in the time price (both one-sided at 5%); H2, the income-interaction (normal-good) test, reported as the confidence interval on mu. H1-H3 are treated as three distinct hypotheses with no family-wise multiplicity correction.
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Other Primary Investigators

Field Before After
Affiliation Jamieson London School of Economics
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Sponsors

Field Before After
Public No Yes
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