Effective Fertility: A New Measure

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***New working paper alert*** With Ari Jacob, I present a new measure of the # of surviving children per female over time & across countries. It shows slower decline globally than total fertility rate (TFR). Show remarkable stability within countries over time. @_alice_evans

Available at nber.org/papers/w33175 and bfi.uchicago.edu/working-papers/effective-fertility-a-new-measure-of-surviving-children-to-analyze-fertility-decline/

TFR measures number of kids each female has. But not all kids survive. We create a measure called effective fertility which is roughly: TFR x probability of survival. Survival is measured either through reproductive years (EFR-R) or theough working years (EFR-L). @lymanstoneky

EFR-R can, conveniently, be approximated by existing demographic concepts like: 1/ Net reproductive rate (reported by UN) 2/ 2 x (Ratio of TFR to replacement level fertility) Even though NRR is not designed to measure surviving kids. Unfortunately, these don't measure EFR-L.

What does EFR reveal? Globally: - 1/3 of changes in TFR since 1950 simply compensate for decline in mortality rates, i.e., don't change EFR - Of the change in EFR, 40% or more cannot be explained by economic factors like income

Historical European data since 1750 show: - Before WW1 EFR is relatively stable, even during demog. transition - EFR collapses after WW1, spike after WW2 - After baby boom, while EFRs fall below 2, they hold stead there So pop growth is slowing, but not at an accelerating pace.

Historical US data show: - Although Blacks have much higher mortality & fertility, Black and White EFR are remarkably similar over time

Both European and US data show cycling of EFR with 20-30 yr periods. Consistent with Easterlin hypothesis that high wages lead to more births, which then expand labor supply and lower wages, leading to lower births in next generation, which elevates wages, leading to more births, and so on.

Comments welcome! People who might life this: @ATabarrok @slatestarcodex @robinhanson @bryan_caplan @GarettJones @elonmusk @DorianAbbot @MoreBirths @Aaronal16 @salonium @lefineder @BirthGauge @kearney_melissa @WorksInProgMag @arpitrage @StatisticUrban @cremieuxrecueil

In future work, we hope to calculate total human capital produced by females, total number of grandkids and of employed persons per female. We'll also explore the wild fluctuation in fertility around calamities like wars & famines, & estimate net impact on future population.

You can read the unrolled version of this thread here: typefully.com/anup_malani/9mvow95