Distinguishing the impact of postponement, spacing and stopping on birth intervals: evidence from a model with heterogeneous fecundity.
Timæus, Ian M;
Moultrie, Tom A;
(2012)
Distinguishing the impact of postponement, spacing and stopping on birth intervals: evidence from a model with heterogeneous fecundity.
Journal of biosocial science, 45 (3).
pp. 311-330.
ISSN 0021-9320
DOI: https://doi.org/10.1017/S0021932012000648
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This paper investigates the impact on birth intervals of three distinct birth control strategies: stopping childbearing, spacing births and the postponement of further childbearing for reasons unrelated to women's family-building histories. A macro-simulation model of the family-building process is described that incorporates heterogeneity in fecundability. This model is used to demonstrate that the postponement of further childbearing has a distinctive impact on schedules of duration-specific fertility rates that differs from that of both family-size limitation and birth spacing. In particular, the simulation results, supplemented by an analytical exposition, show that reductions in fertility due to spacing are a function of interval duration and its log, while reductions due to postponement are a function of interval duration and its square. This provides a way to test statistically for the presence of, and distinguish between, differential postponement and spacing in regression analyses of birth history data.