Table 2. Sex differences in the effect of levels of reproductive investment on lifespan in individuals that survived until age 55 in Utah.

Number of children	estimate	SE	z	p	AF
Females
2–4	0.0053	0.002	2.68	0.007	1.005
5–8	−0.0090	0.002	−4.56	<0.0001	0.99
9–14	–0.028	0.002	−3.23	<0.0001	0.97
15–21	−0.042	0.006	−6.58	<0.0001	0.96
Males
2–4	0.011	0.003	3.73	0.0002	1.011
5–8	0.0091	0.003	3.27	0.001	1.0092
9–14	0.0019	0.003	0.65	0.52	1.0018
15–21	0.0032	0.005	0.70	0.48	1.0032
22–64	−0.0074	0.008	−0.89	0.37	0.99

Shown are parameter estimates (estimate) with associated standard errors (SE), z and p-values for the effect of different levels of reproductive investment obtained from parametric survival models. The acceleration factor (AF) indicates the estimated mean survival time for individuals with increasing parity compared to individuals with one child.