Associate Professor, University of Copenhagen
Visiting Assistant Professor, Brown University
Research Affiliate, Centre for Economic Policy Research (CEPR)
In this article, I provide an overview of the research on a root cause of differences in economic development and other social conditions across world populations. The research exploits the fact that human migration from Africa 60 to 90 thousand years ago affected the global distribution of population diversity to examine the impact of population diversity on economic development, civil war, political institutions, interpersonal trust, and other societal conditions across countries, regions, and ethnicities. Among other things, research has shown that population diversity (i) has a positive effect on per capita income in more homogeneous populations, a negative effect in more heterogeneous populations, and explains between 16% and 26% of the variation in per capita income that cannot be explained by other basic variables, (ii) increases the risk and severity of civil war and civil conflict, and (iii) promotes innovation and reduces interpersonal trust.
I denne artikel giver jeg et overblik over forskningen i en dybtliggende årsag til forskelle i økonomisk udvikling og andre samfundsforhold på tværs af verdensbefolkninger. Forskningen udnytter, at menneskets udvandring fra Afrika for 60 til 90 tusinde år siden har påvirket den globale fordeling af befolkningsdiversitet til at undersøge virkningen af befolkningsdiversitet på økonomisk udvikling, borgerkrig, politiske institutioner, mellemmenneskelig tillid, og andre samfundsforhold på tværs af lande, regioner og folkeslag. Forskningen har blandt andet vist, at befolkningsdiversitet (i) har en positiv virkning på indkomst per indbygger i mere homogene befolkninger, en negativ effekt i mere heterogene befolkninger og forklarer mellem 16% og 26% af den variation i indkomst per indbygger, som ikke kan forklares ved andre grundlæggende variable, (ii) forøger risikoen for, og alvorligheden af, borgerkrig og civile konflikter samt (iii) fremmer innovation og mindsker mellemmenneskelig tillid.
In the study of long-run economic growth, it is common to use historical or geographical variables as instruments for contemporary endogenous regressors. We study the interpretation of these conventional instrumental variable (IV) regressions in a general, yet simple, framework. Our aim is to estimate the long-run causal effect of changes in the endogenous explanatory variable. We find that conventional IV regressions generally cannot recover this parameter of interest. To estimate this parameter, therefore, we develop an augmented IV estimator that combines the conventional regression with a separate regression estimating the degree of persistence in the endogenous regressor. Importantly, our estimator can overcome a particular violation of the exclusion restriction that can arise when there is a time gap between the instrument and the endogenous explanatory variable. We apply our results to estimate the long-run effect of institutions on economic performance and the long-run effect of Protestantism on human capital accumulation. In both cases, we find economically significant long-run effects that are smaller than those in the existing literature, demonstrating that our results have important quantitative implications for the field of long-run economic growth. We also use our framework to examine related empirical techniques. We find that two prominent regression methodologies - using gravity-based instruments for trade and including ancestry-adjusted variables in linear regression models - have related issues of interpretation. In the latter case, this problem can be overcome by including both unadjusted and adjusted measures in the regression model.
The Ancient Origins of the Wealth of Nations Handbook of Historical Economics, North-Holland, Amsterdam, 675–717, 2021
with Q Ashraf and O Galor AbstractPDFBook
This essay explores the deepest roots of economic development. It underscores the significance of evolutionary processes in shaping fundamental individual and cultural traits, such as time preference, risk and loss aversion, and predisposition towards child quality, that have contributed to technological progress, human-capital formation, and economic development. Moreover, it highlights the persistent mark of the exodus of Homo sapiens from Africa tens of thousands of years ago on the degree of interpersonal population diversity across the globe and examines the impact of this variation in diversity for comparative economic, cultural, and institutional development across countries, regions, and ethnic groups.
We explore the existence of a local "resource curse" related to Brazil’s oil, using oil price annual changes interacted with measures of local proximity to oil reserves. We find that locations in Brazil that are closer to an oil field are characterized by a higher level of income per capita, when controlling for a range of potentially confounding factors. Furthermore, in a panel setting, we find that better geographical access to oil fields generates a greater positive effect of oil prices on local income per capita. Moreover, this positive impact of oilfield proximity on the effect of oil prices is enhanced in oil rich states. Importantly, these effects appear to be independent of the amount of oil royalties, suggesting the role of an indirect linkage effect.
This research advances the hypothesis and establishes empirically that interpersonal population diversity, rather than fractionalization or polarization across ethnic groups, has been pivotal to the emergence, prevalence, recurrence, and severity of intrasocietal conflicts. Exploiting an exogenous source of variations in population diversity across nations and ethnic groups, as determined predominantly during the exodus of humans from Africa tens of thousands of years ago, the study demonstrates that population diversity, and its impact on the degree of diversity within ethnic groups, has contributed significantly to the risk and intensity of historical and contemporary civil conflicts. The findings arguably reflect the contribution of population diversity to the non-cohesiveness of society, as reflected partly in the prevalence of mistrust, the divergence in preferences for public goods and redistributive policies, and the degree of fractionalization and polarization across ethnic, linguistic, and religious groups.
Life-history theory suggests that the level of fecundity of each organism reflects the effect of the trade-off between the quantity and quality of offspring on its long-run reproductive success. The present research provides evidence that moderate fecundity was conducive to long-run reproductive success in humans. Using a reconstructed genealogy for nearly half a million individuals in Quebec during the 1608–1800 period, the study establishes that, while high fecundity was associated with a larger number of children, perhaps paradoxically, moderate fecundity maximized the number of descendants after several generations. Moreover, the analysis further suggests that evolutionary forces decreased the level of fecundity in the population over this period, consistent with an additional finding that the level of fecundity that maximized long-run reproductive success was above the population mean. The research identifies several mechanisms that contributed to the importance of moderate fecundity for long-run reproductive success. It suggests that, while individuals with lower fecundity had fewer children, the observed hump-shaped effect of fecundity on long-run reproductive success reflects the beneficial effects of lower fecundity on various measures of child quality, such as marriageability and literacy, and thus on the reproductive success of each child.
Exploiting a genealogy of English individuals living in the 16th to the 19th centuries, this study shows that lower parental reproductive capacity positively affected the socio-economic achievements of offspring. Using the time interval between the date of marriage and the first birth as a measure of reproductive capacity, we show that parental fecundity positively affected the number of siblings and that children of parents with lower fecundity were more likely to become literate and employed in skilled and high-income professions. This suggests there was a trade-off between child quantity and quality in England during the industrial revolution, supporting leading theories of the origins of modern economic growth.
We use duration models on a well-known historical data set of more than 15,000 families and 60,000 births in England for the period 1540-1850 to show that the sampled families adjusted the timing of their births in accordance with the economic conditions as well as their stock of dependent children. The effects were larger among the lower socioeconomic ranks. Our findings on the existence of parity-dependent as well as parity-independent birth spacing in England are consistent with the growing evidence that marital birth control was present in pre-transitional populations.
Post-Malthusian Dynamics in Pre-Industrial Scandinavia Scandinavian Journal of Economics, 118(4), 841–867, 2016
with NF Møller AbstractRePEc
Theories of economic growth hypothesize that the transition from pre-industrial stagnation to sustained growth is associated with a post-Malthusian phase in which technological progress raises income and spurs population growth while offsetting diminishing returns to labor. Evidence suggests that England was characterized by post-Malthusian dynamics preceding the Industrial Revolution. However, given England's special position as the forerunner of the Industrial Revolution, it is unclear if a transitory post-Malthusian period is a general phenomenon. Using data from Denmark, Norway and Sweden, this research provides evidence for the existence of a post-Malthusian phase in the transition from stagnation to growth in Scandinavia.
Picking Winners? The Effect of Birth Order and Migration on Parental Human Capital Investments in Pre-Modern England European Review of Economic History, 17(2), 210–232, 2013
with C Minns, P Wallis and J Weisdorf AbstractRePEc
This paper uses linked apprenticeship-family reconstitution records to
explore the influence of family structure on human capital formation
in preindustrial England. We observe a small but significant
relationship between birth order, resources and human capital
investments. Among the gentry, eldest sons were almost never
apprenticed. Outside the gentry, a large number of apprentices were
eldest sons, even from farming families. This implies a relatively
large place for a child’s aptitude and interest in shaping their
career compared to custom or inheritance practices, making the
"middling sorts" behave much more as families do in present-day labour
studies than the contemporary elites. We also find a surprisingly high
rate of return migration, questioning the emphasis on neo-locality and
suggesting that parents could anticipate benefiting directly from
positive externalities arising from the training provided to
children. This interpretation also fits well with our finding that if
parents had died before indenture, apprentices were significantly less
likely to return home.
The Lasting Damage to Mortality of Early-Life Adversity: Evidence
from the English Famine of the Late 1720s European Review of Economic History, 16(3), 233–246, 2012 (“Editor's Choice”)
with J Weisdorf AbstractRePEc
This paper explores the long-term impact on mortality of exposure to
hardship in early-life. Using survival analysis, we demonstrate that
birth during the great English famine of the late 1720s entailed an
increased death risk throughout life among those who survived the
famine years. Using demographic data from the Cambridge Group's
Population History of England, we find the death risk at age 10 among
the most exposed group - children born to English Midlands families of a
lower socioeconomic rank - is up to 66 percent higher than that of the
control group (children of similar background born in the 5 years
following the famine). This corresponds to a loss of life expectancy
of more than 12 years. However, evidence does not suggest that
children born in the 5 years prior to the famine suffered increased
death risk.
Prices, Wages, and Fertility in Pre-Industrial
England Cliometrica,
6(1), 63–77, 2012 AbstractRePEcJournalPDF
To shed light on the economic-demographic mechanisms operating in the
epoch of pre-industrial economic stagnation, a two-sector Malthusian
model is formulated in terms of a cointegrated vector autoregressive
model on error correction form. The model allows for both agricultural
product wages and relative prices to affect fertility. The model is
estimated using new data for the pre-industrial period in England, and
the analysis reveals a strong, positive effect of agricultural wages
as well as a nonnegative effect of real agricultural prices on
fertility. Furthermore, it is demonstrated that there is strongly
decreasing returns to scale with respect to labour in the agricultural
sector and approximately constant returns to scale in the
manufacturing sector. The analysis provides evidence in favour of the
usual Malthusian model, as invoked by unified growth theories such as
e.g. Galor and Weil (Am Econ Rev 90:806–828, 2000).
Health
Male Fertility Before and After Androgen Abuse The Journal of Clinical Endocrinology & Metabolism, forthcoming
Authors: J Windfeld-Mathiasen, Kim Peder Dalhoff, Jon Trærup Andersen, M Klemp, A Horwitz, Henrik Horwitz AbstractJournal (Open Access)
Purpose: Previous research has found that male users of anabolic steroids (AS) are diagnosed, approximately, twice as often with infertility. We therefore set out to investigate the fertility in men using AS. Methods: The study includes the 545 males who were tested positive for AS in an anti-doping test program in Danish fitness centers during the period January 3rd, 2006 to March 1st, 2018. The confirmed users were matched by birth year with 5,450 male controls. We followed this cohort from ten years prior to testing positive and until the end of follow-up in May 2018. Results: During the ten-year period prior to testing positive the AS user group experienced a 26% lower fertility rate than the controls (rate ratio: 0.74, 95% CI: (0.60-0.90), p=0.0028). However, in the years following the doping sanction, the AS group made a significant catch-up, and at completed follow-up the total fertility rate was only 7% lower than expected (RR 0.93, 95% CI (0.84-1.03). The prevalence of assisted reproduction was 5.69% in the AS group and 5.28% in the control group (p=0.69). Five years after having the diagnosis of infertility 69% had achieved parenthood in the AS group compared to 74% among 68 the controls (p=0.58). Conclusion: the fertility rate among AS users was close to that in the background population, and the 70 study indicates that infertility associated with AS abuse is reversible. The results give hope for AS users 71 suffering from involuntary childlessness.
Brain Responses to Passive Sensory Stimulation Correlate With Intelligence Frontiers in Aging Neuroscience, 11, 2019
Authors: A Horwitz, M Klemp, H Horwitz, M D Thomsen, E Rostrup, E L Mortensen, M Osler, M Lauritzen, K Benedek AbstractJournal (Open Access)
This study investigates the association between intelligence and brain power responses to a passive audiovisual stimulation. We measure the power of gamma-range steady-state responses (SSRs) as well as intelligence and other aspects of neurocognitive function in 40 healthy males born in 1953. The participants are a part of a Danish birth cohort study and the data therefore include additional information measured earlier in life. Our main power measure is the difference in power between a visual stimulation and a combined audiovisual stimulation. We hypothesize and establish empirically that the power measure is associated with intelligence. In particular, we find a highly significant correlation between the power measure and present intelligence scores. The association is robust to controlling for size-at-birth measures, length of education, speed of processing as well as a range of other potentially confounding factors. Interestingly, we find that intelligence scores measured earlier in life (childhood, youth, late midlife), are also correlated with the present-day power measure, suggesting a deep connection between intelligence and the power measure. Finally, we find that the power measure has a high sensitivity for detection of an intelligence score below the average.
The Prognosis Following Amphetamine Poisoning Scandinavian Journal of Public Health, 45, 773–781, 2017
Authors: H Horwitz, K Dalhoff, M Klemp, A Horwitz, J Andersen, G Jürgens AbstractJournal
Aims: This study investigated the long-term mortality following poisoning by amphetamine or substituted amphetamines. Furthermore, we examined the social problems and somatic and psychiatric co-morbidity related to amphetamine poisoning, and their impact on the long-term survival. Methods: We identified amphetamine poisoned patients from the Danish Poison Information Centre database and correlated their personal identification numbers with seven Danish national registries related to different social and health aspects. For each case we sampled 100 age and gender matched controls from the background population. Results: From August 2006 to December 2013 we identified 1,444 patients (70% males) who experienced amphetamine poisoning. Fifty-two percent of the cases were classified as mixed poisonings and the average age at first contact was 24.8 years (SD 8.6). The prevalence of psychiatric disorders, HIV, viral hepatitis, and previous prison incarceration was approximately ten times higher than among healthy controls. After seven years 11% were deceased as opposed to 0.6% in the control group, and 64% of the patients died from unnatural causes. Male gender (HR 2.29, 95% CI (1.07-4.90)), age (HR 1.06, 95% CI (1.03-1.09)), opioid dependence (HR 2.88, 95% CI (1.42-5.85)), schizophrenia (HR 3.09,95% CI (1.63-5.86)), affective disorders (HR 2.65, 95% CI (1.44-4.90)) and HIV (HR 5.45, 95% CI (1.19-24.90)) were associated with a high mortality. Furthermore, a significant proportion of these patients experienced social and health related deterioration in the years following poisoning. Conclusion: Amphetamine poisoning is associated with a poor long-term prognosis and is complicated by additional social and health related issues.
Visual Steady State in Relation to Age and Cognitive Function PLOS ONE, 12(2), 2017
Authors: A Horwitz, M Thomsen, I Wiegand, H Horwitz, M Klemp, M Nikolic, L Rask, M Lauritzen, K Benedek AbstractJournal (Open Access)
Neocortical gamma activity is crucial for sensory perception and cognition. This study examines the value of using non-task stimulation-induced EEG oscillations to predict cognitive status in a birth cohort of healthy Danish males (Metropolit) with varying cognitive ability. In particular, we examine the steady-state VEP power response (SSVEP-PR) in the alpha (8Hz) and gamma (36Hz) bands in 54 males (avg. age: 62.0 years) and compare these with 10 young healthy participants (avg. age 27.6 years). Furthermore, we correlate the individual alpha-to-gamma difference in relative visual-area power (ΔRV) with cognitive scores for the older adults. We find that ΔRV decrease with age by just over one standard deviation when comparing young with old participants (p<0.01). Furthermore, intelligence is significantly negatively correlated with ΔRV in the older adult cohort, even when processing speed, global cognition, executive function, memory, and education (p<0.05). In our preferred specification, an increase in ΔRV of one standard deviation is associated with a reduction in intelligence of 48% of a standard deviation (p<0.01). Finally, we conclude that the difference in cerebral rhythmic activity between the alpha and gamma bands is associated with age and cognitive status, and that ΔRV therefore provide a non-subjective clinical tool with which to examine cognitive status in old age.
Antihypertensive Medication Postpones the Onset of Glaucoma: Evidence from a Nationwide Study Hypertension 69(2), 202–210, 2017
Authors: A Horwitz, M Klemp, J Jeppesen, J Tsai, C Torp-Pedersen, M Kolko AbstractJournalCoverage
The aim was to investigate the impact of anti-hypertensive medication on the onset of glaucoma. Data from the complete Danish population between 40 to 95 years of age were used in the period from 1996 to 2012, covering more than 2.6 million individuals. The National Danish Registry of Medicinal Products Statistics was used to identify all claimed prescriptions for glaucoma medication and anti-hypertensive drugs. We first investigated basic correlations in the data and found that patients treated with anti-hypertensive medication, at any time during the study period, had a significantly higher overall relative risk of glaucoma, even when controlling for age and gender (with a relative risk of 1.31 and p<0.0001). Furthermore, our data confirm the well-known positive association between age and glaucoma. In order to investigate the causal effect of anti-hypertensive treatment on the onset of treatment for glaucoma, we used a regression discontinuity study design. This analysis provides our main finding, namely that prescription of anti-hypertensive medication lead to a significant reduction in the risk of developing glaucoma. Therefore, although hypertension – as indicated by the use of anti-hypertensive medication – is positively correlated with glaucoma, our study indicates that anti-hypertensive medication itself may have a preventive effect on the development of glaucoma.
Selected Working Papers
Roots of Autocracy An updated 2019-version is available. Please e-mail me for details. with O Galor AbstractPDFCoverage
This research explores the origins of the variation in the prevalence and nature of political institutions across the globe. It advances the hypothesis and establishes empirically that diversity across human societies, as determined in the course of the exodus of Homo sapiens from Africa tens of thousands of years ago, contributed to the formation of autocratic institutions across societies. The study suggests that while population diversity has amplified the beneficial effects of institutions in mitigating the adverse effects of non-cohesiveness on productivity, the contribution of diversity to the range of cognitive and physical traits has fostered the scope for domination, leading to the formation and persistence of institutions of the autocratic type. In order to test the proposed hypothesis, this research constructs a novel geo-referenced dataset of population diversity of ethnic groups as well as their geographic, ethnographic, and institutional characteristics. The analysis suggests that diversity contributed to the emergence of autocratic pre-colonial institutions. Moreover, the findings indicate that the impact of diversity on these institutions has plausibly operated through its dual effect on the formation of institutions as well as class stratification. Furthermore, reflecting the persistence of institutional, cultural, and human characteristics, the study suggests that the spatial distribution of population diversity across the globe has also contributed to contemporary variation in the degree of autocracy across countries.
Heterogeneity and Productivity An updated 2019-version is available. Please e-mail me for details. with Q Ashraf and O Galor AbstractRePEc
This research explores the effects of within-group heterogeneity on group-level productivity. It establishes that observed genetic diversity of 230 worldwide ethnic groups, as well as predicted genetic diversity of 1,331 ethnic groups across the globe, has a hump-shaped effect on economic prosperity, reflecting the trade-off between the beneficial and the detrimental effects of diversity on productivity. Moreover, the study demonstrates that variations in within-ethnic-group genetic diversity across ethnic groups contribute to ethnic and thus regional variation in economic development within a country.
The Out of Africa Hypothesis of Comparative Development Reflected by Nighttime Light Intensity An updated 2019-version is available. Please e-mail me for details. with Q Ashraf and O Galor AbstractRePEc
This research establishes that migratory distance from the cradle of anatomically modern humans in East Africa and its effect on the distribution of genetic diversity across countries has a hump-shaped effect on nighttime light intensity per capita as observed by satellites, reflecting the trade-off between the beneficial and the detrimental effects of diversity on productivity. The finding lends further credence to the hypothesis that a significant portion of the variation in the standard of living across the globe can be attributed to factors that were determined in the distant past.
Population Diversity and the Roots of Mistrust with O Galor and Q Ashraf
Other Publications
Further Evidence of Within-Marriage Fertility Control in Pre-Transitional England Demography, 56, 4, 1557–1572, 2019 with F Cinnirella and J Weisdorf
Shedding (night-time) light on the local resource curse VoxEU.org, 2017, with M Gradstein
The biocultural origins of human capital formation and economic growth VoxEU.org, 2014, with O Galor
Empirical Investigations in Unified Growth Theory Department of Economics, University of Copenhagen, PhD Series; ISBN: 9788791342783, 2013
Glossary in
An Economic History of Europe, by KG Persson, Cambridge University Press, 2010
with KG Persson
Presentations
1st International Workshop on Migration and Family Economics, Paris, France, 2022; UCLouvain Economics Seminar, Louvain-la-Neuve, Belgium, 2021; Danish Economic Society's biannual meeting, Kolding, 2020; 13th International Conference on Computational and Financial Econometrics, London, 2019; Bonn University, Germany, December, 2017; Hamburg University, Germany, December, 2017; American Economic Association, Chicago, USA, January, 2017; Association for the Study of Religion, Economics, and Culture, Copenhagen, Denmark, May, 2016; World Economic History Congress, Kyoto, Japan, 2015; Economic Growth Mini Workshop, Copenhagen, Denmark, June, 2015; Towards Sustained Economic Growth: Geography, Demography and Institutions, Barcelona, Spain, June, 2015; MEHR Seminar, Copenhagen, Denmark, May, 2015; Ben-Gurion University, Israel, January, 2015; CESifo Venice Summer Institute: Demographic Change and Long-Run Development, Venice, Italy, July, 2014; Warwick Summer Workshop in Economic Growth, Coventry, England, July, 2014; Society for Economic Dynamics Annual Meeting, Toronto, Canada, June, 2014; Towards Sustained Economic Growth: Geography, Demography and Institutions, Barcelona, Spain, June, 2014; Macro Lunch Seminar, Brown University, USA, September, 2013; Population Studies & Training Center Colloqium, Brown University, USA, September, 2013; 27th Annual Conference of the European Society for Population Economics, University of Aarhus, Denmark, June, 2013; Economic History Workshop, University of Copenhagen, Denmark, May, 2014; 4th Workshop on Growth, History and Development, University of Southern Denmark, Denmark, March, 2013; DGPE Workshop, Denmark, November, 2012; MEHR Seminar, University of Southern Denmark, Denmark, May, 2012; Spring Meeting of Young Economists, Centre for European Economic Research, Germany, April, 2012; 2nd Workshop on Growth, History and Development, University of Copenhagen, Denmark, March, 2012; EPRU Seminar, University of Copenhagen, Denmark, March, 2012; Macro Lunch Seminar, Brown University, United States of America, December, 2011; 2nd Jerusalem Summer School in Economic Growth, Hebrew University, Israel, June/July, 2011; 2nd Workshop on Growth, History and Development, University of Copenhagen, Denmark, April, 2011; Issues in Economic History Seminar, EUI, Italy, November, 2010; Towards Sustained Economic Growth: Evidence and Theory, CREI, Spain, October, 2010; 5th Sound Economic History Workshop, University of Lund, Sweden, October, 2010; Ph.D. Seminar, University of Copenhagen, Denmark, May, 2010; Mini Workshop on Growth and Development, University of Copenhagen, Denmark, May, 2010; MEHR seminar, University of Copenhagen, Denmark, March, 2010; Workshop on Growth, History and Development, University of Copenhagen, Denmark, January, 2010; Oxford FRESH Meeting, University of Oxford, England, December, 2010; Economic History Seminar, University of Lund, Sweden, October, 2010.
Other Work for Download
MATLAB program for numerically solving overlapping generations models
This program is designed to visualize the phase space of Overlapping Generations (OLG) models, even when multiple intertemporal equilibria are present, as demonstrated below. Note that this program does not calculate the model's transition path. The documentation was co-authored with Christian Groth, who has also utilized the program for teaching purposes (link). Examples of the graphics generated by the program are displayed below.
