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HEREDITY, FAMILY & INEQUALITY

HEREDITY, FAMILY & INEQUALITY. Michael Beenstock Hebrew University of Jerusalem January 2011. Francis Galton Died 1911. Discovered regression and correlation 1884 Regression towards the mean in height Beta convergence and sigma convergence Founder of behavioral genetics: Twin studies

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HEREDITY, FAMILY & INEQUALITY

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  1. HEREDITY, FAMILY & INEQUALITY Michael Beenstock Hebrew University of Jerusalem January 2011

  2. Francis GaltonDied 1911 • Discovered regression and correlation 1884 • Regression towards the mean in height • Beta convergence and sigma convergence • Founder of behavioral genetics: Twin studies • Founder of eugenics, fingerprinting and IQ tests • Nature v Nurture: Pro nature & heredity

  3. Correlation within the Family • Intergenerational: parents & children • Intragenerational: siblings • Anthropometry: birth weight, height, BMI • Demography: fertility, longevity, IQ • Social: crime, religiosity, personality • Economics: schooling, earnings, wealth • Earnings: consensus estimate 0.4.

  4. Inequalitybeta & sigma convergence • Yc =  + Yp+ c 0 <  < 1 • Var(Yc) = 2var(Yp) + var(c) • Var(Y) →var()/(1 - 2)

  5. Nature v Nurture • Aristotle & Plato: Nature + Heredity • Locke: tabula rasa (blank slate) v innatism • Darwin: back to nature • Developmental psychology: nurture • Behavioral genetics: nature • Economics: mainly nature

  6. Innatist Controversies • Jenkins (1968) Race & IQ • Wilson (1975) Sociobiology & Humans • Dawkins (1976) Selfish Gene • Herrnstein & Murray (1994) Bell Curve: IQ matters more than family • Harris (1998) Nurture Illusion

  7. Behavioral Genetics • P = G + E • Var(P) = var(G) + var(E) + 2cov(GE) • rGE =cov(GE)/sd(G)sd(E) gene-environment correlation • h2 = var(G)/var(P) heritability (nature) • e2 = var(E)/var(P) (nurturability) • Cov(P1P2)=cov(G1G2)+cov(E1E2)+2cov(E1G2) • r = h2rG + (1 – h2 -2herGE)rE + 2herG1E2

  8. MZ & DZ Twins • rG.MZ = 1 rG.DZ = ½ • rE.MZ = rE.DZ Equal Environments (EEA) • rGE = 0 • rG1E2 = 0 • h2 = 2(rMZ – rDZ) • rMZ = 0.7 rDZ = 0.3 h2 = 0.8 • Alternative assumptions: h2 = 0! • No behavioral theory in behavioral genetics

  9. Adopted & Biological Siblings • rG.A = 0 rG.B = ½ • rE.A = rE.B (EEA) • rGE = 0 etc • h2 = 2(rB – rA) • Random selection into adoption!

  10. Methodological Problems • Genotypes not observed: omitted variable bias • Environments endogenous: simultaneous equations bias • Environments depend on unobserved genotypes: E(Xu) ≠ 0 • I am my sibling’s sibling: Reflection Bias • Solution: IV for environments

  11. Natural Experiments • Environmental effects • Kling et al (2005) Moving to Opportunity • Oreopoulos (2003) Toronto • Edin at al (2003) Immigrants in Sweden • Gould et al (2004) Immigrants in Israel • Shea (1999) Parents’ income in US • Beenstock (2010) Parents’ schooling and income in Israel • Small effect sizes

  12. Measuring Genotypes • Main problem: G is not observed • Y =  + E + θX + u • u = λG + e • E(Eu) = λE(EG) • Generated Regressor Methodology: Beenstock (2007, 2008, 2010) • Mincer residuals measure unobserved earning ability

  13. Genome-wide Association Studies(GWAS) • Human Genome Project 2003: Mapping DNA • 23 chromosomes 3 billion base pairs • Quantitative trait loci (QTL) unobserved • Use genetic markers (SNPs) to measure QTLs • 1 million markers N = 20,000 • Data-mining: low statistical power • Bonferroni t – statistics reduce false positives • Medicine: replication failure • Induction (Bacon) v deduction (Hume)

  14. GWAS & Social Science (Geneonomics)? • Longitudinal Study of Adolescent Health • Health Retirement Survey • Wisconsin Longitudinal Study • A gene for violence? Caspi et al (2002) • A gene for schooling? Beauchamp et al (2011) • A new age is not dawning

  15. Nature – Nurture: So What? • Blank slaters insist the slate is 100% blank • Innatists don’t insist slate is 0% blank • If slate is 0% blank: genetic determinism • Social intervention can’t help • Research so far suggests that environments don’t matter much • Does not mean that genes matter by default

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