Coevolution of farming and private property rights

PNAS May 28, 2013 vol. 110 no. 22

Coevolution of farming and private property during the early Holocene

Samuel Bowles, and Jung-Kyoo Choi

The advent of farming around 12 millennia ago was a cultural as well as technological revolution, requiring a new system of property rights. Among mobile hunter–gatherers during the late Pleistocene, food was almost certainly widely shared as it was acquired. If a harvested crop or the meat of a domesticated animal were to have been distributed to other group members, a late Pleistocene would-be farmer would have had little incentive to engage in the required investments in clearing, cultivation, animal tending, and storage. However, the new property rights that farming required—secure individual claims to the products of one’s labor—were infeasible because most of the mobile and dispersed resources of a forager economy could not cost-effectively be delimited and defended. The resulting chicken-and-egg puzzle might be resolved if farming had been much more productive than foraging, but initially it was not. Our model and simulations explain how, despite being an unlikely event, farming and a new system of farming-friendly property rights nonetheless jointly emerged when they did. This Holocene revolution was not sparked by a superior technology. It occurred because possession of the wealth of farmers—crops, dwellings, and animals—could be unambiguously demarcated and defended. This facilitated the spread of new property rights that were advantageous to the groups adopting them. Our results thus challenge unicausal models of historical dynamics driven by advances in technology, population pressure, or other exogenous changes. Our approach may be applied to other technological and institutional revolutions such as the 18th- and 19th-century industrial revolution and the information revolution today.

Link

Levels of genetic diversity and economic prosperity (?)

Ewen Callaway tips me on the controversy surrounding a new paper which proposes a link between levels of genetic diversity and economic prosperity. I am linking to a version of the paper that is available online, as well as to a response by several geneticists, and a response to the response.

From the abstract, it seems that the authors are suggesting that there is an optimum level of genetic diversity, with either too little or too much of it being harmful for economic development.

Here are my own ideas on the general topic, prior to reading either the paper or the response letter.

Genetic diversity is, in general, a good thing for a population, for a simple reason: adaptation via natural selection depends on the existence of variation (there cannot be selection in the absence of alternatives). Other things being equal, a population possessing a greater amount of genetic diversity has a greater probability of already possessing adaptive alleles that might be necessary to meet new environmental challenges (e.g., pathogens).

But, we must also remember that genetic diversity can be partitioned to what is useful, neutral, or deleterious. We ought to be thankful that our Major Histocompatibility Complex (MHC) region is diverse, largely indifferent whether neutrally involving microsatellite loci have higher or lower allele variance in two populations, and a little concerned if there is an abundance of mildly deleterious rare variants sprinkled in our genomes, or a strong-effect disease-causing variant in one locus.

It is by no means clear whether human populations differ, and how they differ in each of these three components. Too much "neutral" diversity is patently irrelevant for economic prosperity; too much "useful" diversity may be helpful, and too much "deleterious" harmful, but I see no particular reason why populations would substantially differ in these two categories.

And, indeed, even the boundaries between the useful/neutral/deleterious categories are blurred. Deleterious anaemia-causing mutations are known to have benefits of malaria-resistance. Neutral variants may be "useful" ones in waiting: for example, lactase persistent mutants may have existed in the human species for hundreds of thousands of years, appearing and re-appearing by mutation, but it is when they encountered cow's milk and the need to drink it that they shifted from "neutral" to "useful". And, even useful alleles can cease to be so, e.g., the eradication of swamps and malaria in Greece has removed the benefit of malaria-resistence, and left only the harm of anaemia.

A different idea that one might consider is that diversity is sometimes harmful: for example, if you are picking a 4x100 relay team or hiring lumberjacks, or recruiting violinists, you don't especially want a genetically diverse group, but rather a restricted subset of phenotypes, and, inasmuch as phenotypes are influenced by genotypes, a restricted subset of genotypes as well: those with efficient fast twitch muscles, upper-body strength, and good pitch/finger dexterity respectively.

But, society is not a one-trick pony, and economies depend on an assortment of abilities. There is no "optimal human phenotype" that is good for all occupations, and most working societies have found ways to channel their diversity profitably, restricting it when necessary (e.g., picking a particular subset to be soccer players, and another subset to be figher pilots), or expanding it when necessary (e.g., assembling test groups that might mirror society, or the world at large).

Personally, I am sceptical of explanations that invoke long-standing evolutionary differences between populations. Such explanations (e.g., involving differences established during Out-of-Africa, as in this paper) have a hard time explaining "sign changes" in the direction of differences over the last few thousand years: China and Mesopotamia, were, by all accounts much more prosperous than most of Europe within historical memory, and the situation is now reversed -although it may be reversed yet again, if current trends continue, at least in the case of China. The people who erected massive monuments on the Americas do not appear to have been poorer than the Japanese of the time. Egypt used to be a breadbasket of Rome, but is now much poorer than Italy. In ancient times, Germans migrated to southern Europe, and during the 20th century many southern Europeans migrated into Germany.

If Out-of-Africa, 100 thousand years ago, sowed the seeds of differential economic prosperity, then these shifts in fortunes over the last few centuries or millennia are difficult to explain.

But, we also don't know that the pattern of genetic diversity observed in modern humans today is the result of Out-of-Africa. Evidence has been slowly and steadily accumulating, that people who live in different parts of the world today are not necessarily the same people of the ones who lived there a few thousand years ago. Migration and admixture have changed the landscape of human genetic variation: migration by expanding "narrow" genetic pools into much wider territories, and admixture by increasing diversity in contact zones.

So, to summarize:

1. Genetic diversity can be positive, neutral, or deleterious; boundaries between these categories are fluid, and their apportionment in different populations is uncertain.
2. Current differences in economic development are in contrast with such differences in the recent historical past, weakening the case that they stem from events that took place in the distant past (such as Out-of-Africa)
3. Current population differences in genetic diversity may have been established by migration and admixture in the recent past, rather than reflecting on events that took place in the distant past.

So, I am rather unconvinced of the hypothesis advanced by Ashraf and Galor. If I find something to add after reading their paper, I will add it here as an update.

RePEc:bro:econwp:2010-7

The "Out of Africa" Hypothesis, Human Genetic Diversity, and Comparative Economic Development

Quamrul Ashraf, Oded Galor

This research argues that deep-rooted factors, determined tens of thousands of years ago, had a significant effect on the course of economic development from the dawn of human civilization to the contemporary era. It advances and empirically establishes the hypothesis that in the course of the exodus of Homo sapiens out of Africa, variation in migratory distance from the cradle of humankind to various settlements across the globe affected genetic diversity and has had a direct long-lasting effect on the pattern of comparative economic development that could not be captured by contemporary geographical, institutional, and cultural factors. In particular, the level of genetic diversity within a society is found to have a hump-shaped effect on development outcomes in the pre-colonial era, reflecting the trade-off between the beneficial and the detrimental effects of diversity on productivity. Moreover, the level of genetic diversity in each country today (i.e., genetic diversity and genetic distance among and between its ancestral populations) has a similar non-monotonic effect on the contemporary levels of income per capita. While the intermediate level of genetic diversity prevalent among the Asian and European populations has been conducive for development, the high degree of diversity among African populations and the low degree of diversity among Native American populations have been a detrimental force in the development of these regions. Further, the optimal level of diversity has increased in the process of industrialization, as the beneficial forces associated with greater diversity have intensified in an environment characterized by more rapid technological progress.

Link

Response to Ashraf and Galor 'The Out of Africa Hypothesis, Human Genetic Diversity and Comparative Economic Development'

Jade D'Alpoim Guedes et al.

Abstract:

This short reply summarizes the concerns of the anthropological community about Ashraf and Galor's (Forthcoming) article in the American Economic Review.

Link

Response to Comments made in a Letter by Guedes et al. on “The Out of Africa Hypothesis, Human Genetic Diversity and Comparative Development”

Link (pdf)

Does capitalism reduce fitness?

I was much surprised to find this blog post on my feed today:

nielsen lab, occupy, and berkeley protests

I don't have much to say about the Occupy movement itself. People can differ in their opinions about the causes of the current economic malaise, and to argue about them. But, I will comment on a point:

We’ve thus been taking part in multiple ‘Occupy’ activities, starting the first meeting of Occupy Oakland in mid-October, marches in SF, and the Nov 2 Oakland general strike. This was a great moment – young and old, blue and white collar workers walked and rejoiced together the whole day. Our sign said ‘rEvolutionary Biologists say: Capitalism Reduces Fitness!’

Well, it’s the objective truth. An flyer distributed in the demonstration was pointing out that an African-American boy born in West Oakland has 15 shorter life expectancy than someone born up in the hills. If that’s not reduction in fitness, what is?

A reduction of life expectancy by 15 years is not evidence of reduction of fitness. Fitness is measured in offspring, it is not measured in years lived. African countries, for example, have very high population growth rates, and very low life expectancies. That is fitness. Fitness is not a comfortable long life, but having lots of babies and living long enough to ensure their survival as independent entities.

It is strange that evolutionary biologists from a top institution would make such a simple mistake. Perhaps public spending is not the best way to advance science and education?

Medieval GDP per capita

On the left there are some interesting tables from the paper.

I don't know how accurate of GDP per capita is that far in the past, as a certain number of assumptions must come into play. However, these numbers should give pause to anyone who makes broad statements about different populations' innate ability based on their present- or recent economic output, especially when such inferences are pushed thousands of years into the past.

The paper also has some estimates of population and population growth rates which should be interesting for population geneticists in calibrating their models.

Medieval England Twice as Well Off as Today’s Poorest Nations

New research led by economists at the University of Warwick reveals that medieval England was not only far more prosperous than previously believed, it also actually boasted an average income that would be more than double the average per capita income of the world's poorest nations today.

Wealth and people and the invasion of alien species

This is an open access paper.

PNAS doi:10.1073/pnas.1002314107

Disentangling the role of environmental and human pressures on biological invasions across Europe

Petr Pyšek et al.

The accelerating rates of international trade, travel, and transport in the latter half of the twentieth century have led to the progressive mixing of biota from across the world and the number of species introduced to new regions continues to increase. The importance of biogeographic, climatic, economic, and demographic factors as drivers of this trend is increasingly being realized but as yet there is no consensus regarding their relative importance. Whereas little may be done to mitigate the effects of geography and climate on invasions, a wider range of options may exist to moderate the impacts of economic and demographic drivers. Here we use the most recent data available from Europe to partition between macroecological, economic, and demographic variables the variation in alien species richness of bryophytes, fungi, vascular plants, terrestrial insects, aquatic invertebrates, fish, amphibians, reptiles, birds, and mammals. Only national wealth and human population density were statistically significant predictors in the majority of models when analyzed jointly with climate, geography, and land cover. The economic and demographic variables reflect the intensity of human activities and integrate the effect of factors that directly determine the outcome of invasion such as propagule pressure, pathways of introduction, eutrophication, and the intensity of anthropogenic disturbance. The strong influence of economic and demographic variables on the levels of invasion by alien species demonstrates that future solutions to the problem of biological invasions at a national scale lie in mitigating the negative environmental consequences of human activities that generate wealth and by promoting more sustainable population growth.

Link

Soil and climate as economic destiny

Figure 1 (on the left) Modelled “suitability” (probability of occurrence, Maxent) for (A) agriculture, (B) sedentary animal husbandry, (C) nomadic pastoralism, and (D) hunting and gathering.

From the paper:

Our simplistic exercise showed that a “geo-deterministic” approach can predict surprisingly many features of human cultural geography without any explicit cultural or historical assumptions. Although many deviations require further factors for a satisfying explanation, the nature of these deviations invite the generation of hypotheses for further research. Our ‘null model’ offers a highly parsimonious, empirically supported explanation to the question of why some regions are more “powerful” than others, supplementing the idea of a historical effect operating through the timing of transition to agriculture [2].

In some instances, our model may actually provide a simpler explanation. Putterman [10], for example, suggested that the dominance of Western European cultures indicates the transmission of “civilization” traits (other than knowledge on agriculture) from regions of first domestication. Our data indicate that higher climatic suitability may have been sufficient for Europe to “catch up”, allowing for much higher population densities than, e.g., the “fertile crescent” region. Models of “suitability” under past climatic scenarios may be helpful to evaluate this. Similarly, models applied to predicted future climatic scenarios may be useful to anticipate changes of the economic suitability of landuse types.

However, our model has clear deviations in some regions that may well be explicable by the availability of animals and plants suitable for domestication (e.g., central Africa). Apart from that, and more importantly, we know that human societies and economies went through historical development, so ignoring history may not always be the best strategy to understand causalities. This problem occurs also with other research questions in biogeography, e.g. when investigating global biodiversity patterns [45]–[47]. Nevertheless, our ‘null model’ will be a useful tool in identifying regions that require further investigation to understand additional processes that shape the distribution and performance of human economic traits.

I really like this type of paper that looks at a simple explanation for a phenomenon, in this case, economic output as a product of soil/climate quality and suitability. As the authors point out, their "null" model has its limitations, and it is precisely in regions of the world where its predictions do not match the observations, that we should look for additional factors (besides soil and climate) to explain economic traits.

Related: Soil and Greek temples.

PLoS ONE 5(5): e10416. doi:10.1371/journal.pone.0010416

Is the Spatial Distribution of Mankind's Most Basic Economic Traits Determined by Climate and Soil Alone?

Jan Beck, Andrea Sieber

Abstract

Background
Several authors, most prominently Jared Diamond (1997, Guns, Germs and Steel), have investigated biogeographic determinants of human history and civilization. The timing of the transition to an agricultural lifestyle, associated with steep population growth and consequent societal change, has been suggested to be affected by the availability of suitable organisms for domestication. These factors were shown to quantitatively explain some of the current global inequalities of economy and political power. Here, we advance this approach one step further by looking at climate and soil as sole determining factors.

Methodology/Principal Findings
As a simplistic ‘null model’, we assume that only climate and soil conditions affect the suitability of four basic landuse types – agriculture, sedentary animal husbandry, nomadic pastoralism and hunting-and-gathering. Using ecological niche modelling (ENM), we derive spatial predictions of the suitability for these four landuse traits and apply these to the Old World and Australia. We explore two aspects of the properties of these predictions, conflict potential and population density. In a calculation of overlap of landuse suitability, we map regions of potential conflict between landuse types. Results are congruent with a number of real, present or historical, regions of conflict between ethnic groups associated with different landuse traditions. Furthermore, we found that our model of agricultural suitability explains a considerable portion of population density variability. We mapped residuals from this correlation, finding geographically highly structured deviations that invite further investigation. We also found that ENM of agricultural suitability correlates with a metric of local wealth generation (Gross Domestic Product, Purchasing Power Parity).

Conclusions/Significance
From simplified assumptions on the links between climate, soil and landuse we are able to provide good predictions on complex features of human geography. The spatial distribution of deviations from ENM predictions identifies those regions requiring further investigation of potential explanations. Our findings and methodological approaches may be of applied interest, e.g., in the context of climate change.

Link

Body mass index and income in Europe

There seems to be some variation in the strength of the effect, but overall the finding is that women with higher BMI (heavier for their height) tend to make less money than slimmer women.

Economics and Human Biology doi:10.1016/j.ehb.2009.01.006

Income and Body Mass Index in Europe

Jaume García Villar and Climent Quintana-Domeque

Abstract

The problem of obesity is alarming public health authorities around the world. Therefore, it is important to study its determinants. In this paper, we explore the empirical relationship between household income and body mass index (BMI) in nine European Union countries. Our findings suggest that, in general, the association is negative for women and nonexistent for men. Moreover, once we decompose household income into “own labor earnings” and “other household income”, we find that the different relationship for men and women appears to be driven by the negative relationship between BMI and “own labor earnings” for women.

Link

Sons of billionaires

From the paper:

For species where one sex has more variable reproductive success (males in polygynous species), the TWH predicts that 1) a mother with more resources to invest would be advantaged by producing a son, as a successful son would out-compete a successful daughter (constrained to a less variable reproductive rate), and 2) a mother with less resources to invest would be advantaged by producing a daughter, as her daughter would out-reproduce an unsuccessful son. Alternatively, if sons are more costly than daughters, only mothers in good condition could bear this cost [2].

PLoS ONE doi: 10.1371/journal.pone.0004195

A Trivers-Willard Effect in Contemporary Humans: Male-Biased Sex Ratios among Billionaires

Elissa Z. Cameron, Fredrik Dalerum

Abstract

Background

Natural selection should favour the ability of mothers to adjust the sex ratio of offspring in relation to the offspring's potential reproductive success. In polygynous species, mothers in good condition would be advantaged by giving birth to more sons. While studies on mammals in general provide support for the hypothesis, studies on humans provide particularly inconsistent results, possibly because the assumptions of the model do not apply.

Methodology/Principal Findings

Here, we take a subset of humans in very good condition: the Forbe's billionaire list. First, we test if the assumptions of the model apply, and show that mothers leave more grandchildren through their sons than through their daughters. We then show that billionaires have 60% sons, which is significantly different from the general population, consistent with our hypothesis. However, women who themselves are billionaires have fewer sons than women having children with billionaires, suggesting that maternal testosterone does not explain the observed variation. Furthermore, paternal masculinity as indexed by achievement, could not explain the variation, since there was no variation in sex ratio between self-made or inherited billionaires.

Conclusions/Significance

Humans in the highest economic bracket leave more grandchildren through sons than through daughters. Therefore, adaptive variation in sex ratios is expected, and human mothers in the highest economic bracket do give birth to more sons, suggesting similar sex ratio manipulation as seen in other mammals.

Link

Nicholas Christakis on the Anthroposphere

An interesting answer from the Edge World Question Center 2009. The part in italics reminds me of a previous post I made on Rise of diseases in modern societies is not (usually) due to genetic or environmental factors:

This is a simple consequence of the one reality of life, namely death. The total mortality of the population is always 100%, as we all eventually die. Therefore the prevalence of a particular disease (which brings us closer to death) does not depend exclusively on factors (genetic or environmental) that cause the disease. It also depends on other diseases or lethal factors which might beat them to the punch.

In previous centuries for example, death during childbirth, tuberculosis, death in war, famine etc. were more prevalent. Thus, they took a larger part of the 100% pie. Degenerative diseases were thus correspondingly less important, because irrespective of genes or environments affecting them, we used to die of other causes.

Here is Christakis on the Anthroposphere:

NICHOLAS A. CHRISTAKIS
Physician and social scientist, Harvard

THE ANTHROPOSPHERE

...

The global population stood at one million at 10,000 BC, 50 million at 1,000 BC, and 310 million in 1,000 AD. It stood at about one billion in 1800, 1.65 billion in 1900, and 6.0 billion in 2000. Analysis of these macro-historical trends in human population usually focuses on this population growth and on the "demographic transition" underlying it.

During the first stage of the demographic transition, life—as Hobbes rightly suggested—was nasty, brutish, and short. There was a balance between birth rates and death rates, and both were very high (30-50 per thousand people per year). The human population grew less than 0.05% annually, with a doubling time of over 1,000 years. This state of affairs was true of all human populations everywhere until the late 18th century.

Then, during the second stage, the death rate began to decline—first in northwestern Europe, but then spreading over the next 100 years to the south and east. The decline in the death rate was due initially to improvements in food supply and in public health, both of which reduced mortality, particularly in childhood. As a consequence, there was a population explosion.

During the third stage, birth rates dropped for the first time in human history. The prior decline in childhood mortality probably prompted parents to realize they did not need as many children; and increasing urbanization, increasing female literacy, and (eventually) contraceptive technology also played a part.

Finally, during the fourth stage—in which the developed world presently finds itself—there is renewed stability. Birth and death rates are again in balance, but now both are relatively low. Causes of mortality have shifted from the pre-Modern pattern dominated by infectious diseases, perinatal diseases, and nutritional diseases, to one dominated by chronic diseases, mental illnesses, and behavioral conditions.

This broad story, however, conceals as much as it reveals. There are other demographic developments worldwide beyond the increasing overall size of the population, developments that are still unfolding and that matter much more. Changes in four aspects of population structure are key: (1) sex ratio, (2) age structure, (3) kinship systems, and (4) income distribution.

Sex ratios are becoming increasingly unbalanced in many parts of the world, especially in China and India (which account for 37% of the global population). The normal sex ratio at birth is roughly 106 males for every 100 females, but it may presently be as high as 120 for young people in China, or as high as 111 in India. This shift, much discussed, may arise from preferential abortion or the neglect of baby girls relative to boys. Gender imbalance may also have other determinants, such as large-scale migration of one or the other sex in search of work. This shift has numerous implications. For example, given the historical role of females as caregivers to elderly parents, a shortage of woman to fill this role will induce large-scale social adjustments. Moreover, an excess of low-status men unable to find wives results in an easy (and large) pool of recruits for extremism and violence.

This shift in gender ratios may have other, less heralded implications, however. Some of our own work has suggested that this shift may actually shorten men’s lives, reversing some of the historic progress we have made. Across a range of species, skewed sex ratios result in intensified competition for sexual partners and this induces stress for the supernumerary sex. In humans, it seems, a 5% excess of males at the time of sexual maturity shortens the survival of men by about three months in late life, which is a very substantial loss.

On the other hand, the population worldwide is getting older, especially in the developed world. Globally, the UN estimates that the proportion of people aged 60 and over will double between 2000 and 2050, from 10% to 21%, and the proportion of children will drop from 30% to 21%. This change also has numerous implications, including on the "dependency ratio," meaning that fewer young people are available to provide for the medical and economic needs of the elderly. Much less heralded, however, is the fact that war is a young person’s activity, and it is entirely likely that, as populations age, they may become less aggressive.

The changing nature of kinship networks, such as the growth in blended families—whether due to changing divorce patterns in the developed world or AIDS killing off parents in Africa—has implications for the network of obligations and entitlements within families. Changing kinship systems in modern American society (with complex mixtures of remarried and cohabiting couples, half-siblings, step-siblings, and so on) are having profound implications for caregiving, retirement, and bequests. Who cares for Grandma? Who gets her money when she dies?

Finally, it is not just the balance between males and females, or young and old, that is changing, but also the balance between rich and poor. Income inequality is reaching historic heights throughout the world. The top 1% of the people in the world receives 57% of the income. Income inequality in the US is presently at its highest recorded levels, exceeding even the Roaring Twenties. And while economic development in China has proceeded with astonishing rapidity, income is not evenly distributed; the prospects for conflict in that country as a result seem very high in the coming decades.

Lacking any real predators, a key feature of the human environment is other humans. In our rush to focus on threats such as global warming and environmental degradation, we should not overlook this fact. It is well to look around at who, and not just what, surrounds us. Population structure will change everything. Our health, wealth, and peace depend on it.

Sexual orientation and personal income

The results of this study are consistent with the hypothesis that "homosexuality is rooted in a side-effect of the expression of femininity-- or masculinity-enhancing traits in individuals of the wrong gender". Men generally make more money than women, so it is expected that men who are more feminine biologically will make less money, while women who are more masculine will make more money (on average).

Homosexual men have significantly lower personal incomes than heterosexual individuals

Homosexual women have higher incomes than straight women

Montreal, Canada – October 29, 2008 – A new study in the Canadian Journal of Economics provides the first evidence on sexual orientation and economic outcomes in Canada. The study found that gay men have 12 percent lower personal incomes and lesbians have 15 percent higher personal incomes than heterosexual men and women.

Christopher S. Carpenter of The Paul Merage School of Business at the University of California Irvine used data from the Canadian Community Health Survey which includes standard demographic questions as well as self-reports on sexual orientation.

Like previous patterns found in the U.S. and the U.K., results show that gay men have significantly lower personal incomes than similarly situated straight individuals, while lesbians have significantly higher personal incomes than straight women.

Also, similar to gay and straight differences in the U.S., gay men and lesbians in Canada are more likely to live in urban areas and more highly educated than heterosexuals in Canada.

"This is the first work to document statistically and economically meaningful differentials associated with sexual orientation in Canada," Carpenter concludes. "The long-term significance of the study will be to further the call for more research into the causes and consequences of gay/straight differences in Canada and elsewhere."

Canadian Journal of Economics doi: 10.1111/j.1540-5982.2008.00502.x

Sexual orientation, work, and income in Canada

Carpenter, Christopher S.

We provide the first evidence on sexual orientation and economic outcomes in Canada using confidential data that ask adults a direct question about their sexual orientation. Gay men have 12% lower personal incomes and lesbians have 15% higher personal incomes than otherwise similar heterosexual men and women, respectively. Different labour force patterns can account for some of the income differentials. We also document large differences in educational attainment, childrearing, and urbanicity that generally mirror patterns found in the US. Finally, we show that applying couples-based approaches common in this literature greatly overstates the magnitudes of gay/straight income gaps.

Link

IQ and Wealth

Intelligence (Article in Press)

Do you have to be smart to be rich? The impact of IQ on wealth, income and financial distress

Jay L. Zagorskya et al.

Abstract

How important is intelligence to financial success? Using the NLSY79, which tracks a large group of young U.S. baby boomers, this research shows that each point increase in IQ test scores raises income by between $234 and $616 per year after holding a variety of factors constant. Regression results suggest no statistically distinguishable relationship between IQ scores and wealth. Financial distress, such as problems paying bills, going bankrupt or reaching credit card limits, is related to IQ scores not linearly but instead in a quadratic relationship. This means higher IQ scores sometimes increase the probability of being in financial difficulty.

Link

Pioneering study shows richest 2 percent own half world wealth

From the EurekAlert public release:

The richest 2% of adults in the world own more than half of global household wealth according to a path-breaking study released today by the Helsinki-based World Institute for Development Economics Research of the United Nations University (UNU-WIDER).

The most comprehensive study of personal wealth ever undertaken also reports that the richest 1% of adults alone owned 40% of global assets in the year 2000, and that the richest 10% of adults accounted for 85% of the world total. In contrast, the bottom half of the world adult population owned barely 1% of global wealth.

The research finds that assets of $2,200 per adult placed a household in the top half of the world wealth distribution in the year 2000. To be among the richest 10% of adults in the world required $61,000 in assets, and more than $500,000 was needed to belong to the richest 1%, a group which — with 37 million members worldwide — is far from an exclusive club.

And from the BBC:

The richest 2% of adults in the world own more than half of all household wealth, according to a new study by a United Nations research institute.

The report, from the World Institute of Development Economics Research at the UN University, says that the poorer half of the world's population own barely 1% of global wealth.

There have of course been many studies of worldwide inequality.

But what is new about this report, the authors say, is its coverage.

It deals with all countries in the world - either actual data or estimates based on statistical analysis - and it deals with wealth, where most previous research has looked at income.

What they mean by wealth in this study is what people own, less what they owe - their debts. The assets include land, buildings, animals and financial assets.