Global IQ: 1950–2050
Doesn't it seem like the world is getting dumber with
every passing year? Well, maybe it is!
IQ and the Wealth of Nations,
report large differences, amounting to more than two standard deviations,
in the mean IQ of the populations of different countries around the
world, and find that these mean population IQ scores correlate
more strongly with economic development as measured by gross
domestic product (GDP) per capita and long term economic
growth than any other single factor.
It has been widely observed that the birthrate of countries
to fall as they become more wealthy. Most countries in Western Europe
now have birthrates below the replacement rate; in the absence of
immigration, their populations can be expected to fall in the future.
Putting these two pieces of information together, one might expect that
since low IQ countries tend to be less wealthy, they should also be expected
to have higher birthrates than countries with high IQ. If population IQ
and wealth remain constant, the average IQ of the world should then fall over time,
since a larger portion of population growth will occur in low IQ countries.
|| Mean IQ
There are a lot of assumptions going into this conclusion,
starting out with what IQ measures and what, if anything, it
means. See the
“Quarrels, Questions, and Answers”
section below for
discussion of some of these issues.
The animation above (you can view the chart for a given year by selecting
it from the Chart box below the image) shows the global histogram
of IQ and global mean IQ for the hundred year period from 1950 through
2050. Mean population IQ is taken from Lynn and Vanhanen's figures
and yearly population estimates for each country from the
U.S. Census Bureau
Data Base 2003. Taking these figures at face value, we
find that world population and mean IQ evolve at 25 year intervals
over the century as given in the table at the right.
The mean IQ of 185 countries, measured and estimated in
were taken as the invariant IQ of each country over the 1950–2050 time
period. (The figures are given in terms of
countries existing as of the year 2000. For countries which came into being
in the preceding 50 years due to decolonisation, breakup of the Soviet
Union, etc., years prior to independence refer to the
territory with borders identical to the present-day country. The list
of countries includes Hong Kong and Taiwan, considered in
some sense provinces of China, but with large populations,
well measured demographically, and economic performance distinctly
different from that of the People's Republic; and Puerto Rico, a
United States territory with different demographics than the
parent country. The remaining 182 countries include all independent
countries with populations greater than 50,000 with the exception of
Bosnia and Herzegovina, for which no data were available due to the
conflict throughout most of the 1990s.)
The 100 year population history and forecast for the 185
countries with measured or estimated mean IQ was obtained from
U.S. Census Bureau
Data Base 2003, using the mid-year population estimate or projection
for each year.
For each year in the hundred year period, each country's
estimated population for that year was apportioned into bins of
5 IQ points using a normal distribution with the mean IQ for
the country from Lynn and Vanhanen and the 15 point standard deviation
defined for IQ scores. These country histogram bins were summed
to create a global histogram for each year. Global mean IQ was
computed by an average of country IQs weighted by their population.
- Don't differing IQ figures for various countries
simply measure cultural bias in the tests?
- This is a possibility, and in certain cases undoubtedly
plays a factor. Yet tests carefully designed to exclude
cultural bias (for example, spatial relationship tests
based entirely on pictures, memorisation of digit
sequences, and pure eye-hand reaction time) produce
results comparable to those of traditional IQ tests.
Further, if IQ tests embody cultural biases of
the largely U.K. and U.S. creators of the tests, it's
odd that populations of East Asian countries, with a variety
of very different cultures, all test higher than
those of the test makers.
- Won't economic development reduce the rate of population growth
in the low-IQ countries?
- Future population estimates for countries in the Census Bureau
database already take this into account. These are, of course,
consensus estimates which do not take into effect such
impossible-to-forecast circumstances as environmental crises,
plague, bad asteroid days, or, on the other hand, technological
breakthroughs which accelerate economic development in third
world countries. Looking 50 years ahead, only rapid demographic
shifts in the near term will have much impact on the figures for
2050, since the parents of adults of that year are already
mostly alive today.
- Lynn and Vanhanen only actually have IQ data for 81 countries
and they've estimated the rest. How reliable are those estimates?
- I don't know. In most cases their estimates were made by averaging
known IQs of adjacent countries with similar demographic mix. In the
few cases of countries with ethnically diverse populations, they
estimated IQ based on a weighted average of IQs of the country of
origin of each group. They tested this process by using it to
estimate IQ of several countries with known IQ and the results
correspond well with the measured IQs of those countries. Still,
one should bear in mind that 56% of the country IQ figures are
estimated, and not based on any actual in-country measurement at all.
- And those 81 countries they have IQ data for—there seem to be
an awful lot of fudge factors used in computing the numbers they
cite in the tables. How trustworthy are they?
- Fudge factors? Indeed…more than 25 pages
are devoted to explaining the “adjustments”,
“corrections”, “calibrations”, and “weightings” which
go into that table of 81 numbers. The state of the raw
data is more or less hideous. There is no regular,
standardised measurement of IQ in nations of the
world. One is forced to use sporadic studies,
published at widely spaced intervals, using a variety
of tests with more or less cultural bias, on
populations which may exhibit a variety of selection
effects. (For example, if you only test high school
children in a country where 75% of children do not
attend high school, you can't expect your results to be
representative of the population as a whole.) Still,
if you want to do this research, you have work with the
data at hand.
If population mean IQ indeed correlates strongly with economic performance,
then measuring IQ figures for developing countries and studying ways to
increase IQ could play an important rôle in development assistance.
program to regularly measure IQ of, say, 16 year olds in all
countries could provide hard data and, potentially, by permitting
assessment of the effectiveness of programs such as nutrition aid
for mothers and infants, educational initiatives, etc., do a world
of good. Alas, this entire topic is so politically radioactive there
is little likelihood of this ever happening.
- You're assuming the mean IQ of countries won't change over
the hundred year period. How valid is that assumption?
- Apart from the Flynn effect (discussed below), which doesn't
seem to have much effect on the relative IQs of
countries, in cases where the data are available, national
mean IQ does not seem to have varied much over the last 50
years. As long as the population makeup and general circumstances
of a country don't change, it's reasonable to expect the mean IQ for a given
country to remain much the same over the next 50 years. Population migration,
however, can have substantial effects and is not taken into
account in these data. The Census Bureau population estimates
include migration, but the assumption of constant mean IQ may be
invalid when the population of a given country consists of a large
fraction of immigrants from regions with different mean IQ. This is
particularly the case for Western Europe, where the indigenous
population has fertility below the replacement rate, and
the population includes an increasing proportion of immigrants
predominantly from regions with lower mean IQ. To the extent
immigrants have more children per family than the original
population, the effect is magnified. Whether immigrant populations
converge toward the original IQ of their new country as they
assimilate is an open question. In all, since most present day
and anticipated future population migration is from lower
IQ to higher IQ countries, assuming constant IQ probably biases
the global mean forecasts toward the high end.
- Won't the Flynn effect compensate for the downward demographic
shift in IQ?
is an undisputed yet enigmatic aspect of IQ testing.
Shortly after the first IQ tests were standardised, it
was observed that the scores of those taking them
tended to rise from year to year, as much as 15 points
(one standard deviation) per generation. To maintain a
mean score of 100 for the population on which IQ tests
were standardised, test makers were forced to make
their tests increasingly difficult over the
years. In other words, to get the same IQ score as
your father, you must perform equally well on a
substantially tougher test than he took.
If, for whatever reason, everybody were
getting smarter, this would be wonderful news indeed. But a glance
at the numbers shows that something very curious must be going on
here. If IQ were, in fact, rising at a rate of 15 points per
generation then, if the mean IQ of today is 100, that of our
grandparents' generation would have been about 70—generally
considered the threshold of mental retardation.
Clearly, anybody who's spent time with their grandparents
and other folks of that generation knows that's utter
The literature and music of a century
or more ago is clearly not the work of marginally
retarded minds, and its abundance indicates those who wrote it
were not rare exceptions in a generally dull population.
Consider genius in the past. Most people considered geniuses
have IQs in the vicinity of 150, or 3 1/3 standard deviations
above the mean IQ of 100. In a population with a mean IQ of 100,
individuals with IQs of 150 occur with a
of about one in 2300 people—they're rare, but every medium-sized town has
one or more, and even a small country with a population of one
million has more than 425 such geniuses.
Now, in a population with a mean IQ of 70, which naïve interpretation
of the Flynn effect would deem our grandparents to have had, genius-level
IQs of 150 would be 5 1/3 standard deviations above the mean
and occur, on average, in only one out of 20,396,324 people. If we
take the Flynn effect as 3 IQ points per decade, then we'd expect
a mean IQ of 70 around the year 1900. In 1900, the world population
was about 1.7 thousand million, which would imply there were only 80
people with genius-level IQs in the entire world of 1900. The merest
glance at the history of that era will reveal how ridiculous a supposition
Adults, whatever their opinion may be of
“what's the matter with kids today”, are most unlikely to cite
“they're just too doggone smart!” So, the Flynn effect
is a conundrum: a wide variety of tests which agree with one
another and reliably predict outcomes we identify with
“intelligence” all indicate that the general population is
becoming more intelligent at an almost dizzying rate, while
other evidence for this (for example, individuals
with Einstein-calibre intelligence being almost 10,000 times
more common than a hundred years ago) is notably absent. There is
no shortage of hypotheses for what's going on, but little evidence
to support any of them. Flynn himself believes that IQ tests
measure test-taking and problem-solving ability, not genuine
intelligence, and that this has risen over time as more and more
children receive compulsory education and are subjected to
ever more tests. Improved nutrition over the 20th century is often
cited as a factor, as well as the introduction of egalitarian
welfare state systems in developed countries tending to reduce
poverty. But all of these are factors which one would expect
to eventually reach a plateau, and that doesn't seem to have
happened, at least so far.
This isn't a document about the Flynn effect (although it risks becoming
one unless I wind this up rather soon), and since no solution to this
long-standing puzzle is at hand, one can only speculate on what it
really means. Since correction for the Flynn effect is substantial
in Lynn and Vanhanen's national IQ estimates, and can be expected
to strongly influence IQ scores published in the future, it is essential
one bear it in mind in any analysis of population intelligence trends.
- IQ scores are normalised for a mean of 100 and standard deviation of
15 in the populations for which they were originally developed.
Is the standard deviation the same in populations with
higher or lower mean IQ?
- I don't know. This is a fascinating question about which I have found
no research whatsoever. Absent any information to the
contrary, in computing the global IQ histogram in the
charts at the top of this document, I assume a standard
deviation of 15 points regardless of the mean. Note
that this assumption only affects the shape of
the histogram; the global mean is independent of the
variance of individual country populations.
Data Sources for this Page
- Lynn, Richard and Tatu Vanhanen.
IQ and the Wealth of Nations.
Westport, CT: Praeger, 2002.
- Lynn, Richard and Tatu Vanhanen.
and the Wealth and Poverty of Nations”. 2000–2002.
- U.S. Census Bureau.
Data Base 2003.
- U.S. Central Intelligence Agency.
World Factbook 2003.
IQ Phenomenology: The Flynn Effect
- Neisser, Ulric, ed.
The Rising Curve: Long-Term Gains in IQ and Related Measures.
Washington: American Psychological Association, 1998.
- Flynn, J. R.
“The Mean IQ of Americans: Massive gains 1932 to 1978”,
Psychological Bull. 95, 29 (1984).
- Flynn, J. R.
“Massive IQ gains in 14 nations: What IQ tests really measure”,
Psychological Bull. 101, 171 (1987).
- Flynn, J. R.
“IQ gains over time”,
in Sternberg, Robert J.. ed.
Encyclopedia of Human Intelligence.
New York: Macmillan, 1994.
“IQ Exists and Matters” Arguments
- Herrnstein, Richard J. and Charles Murray.
The Bell Curve.
New York: The Free Press,  1996.
- Jensen, Arthur R.
The g Factor: The Science of Mental Ability.
Westport, CT: Praeger, 1998.
- Rushton, J. Philippe.
Intelligence, and the Brain: The Errors and
Omissions of the `Revised' Edition of S. J. Gould's
The Mismeasure of Man (1996)”,
Person. individ. Diff. 23, 169 (1997).
“IQ Doesn't Exist and/or Matter” Arguments
- Gould, Stephen Jay.
The Mismeasure of Man.
New York: W. W. Norton, 1996.
- Devlin, Bernie et al., eds.
Intelligence, Genes, and Success: Scientists Respond to The Bell Curve.
New York: Copernicus, 1997.
- Fraser, Steven.
The Bell Curve Wars.
New York: Basic Books, 1995.
Economic Development and Population Trends
- Todd, Emmanuel.
Paris: Gallimard, 2002.
After the Empire.
New York: Columbia University Press, 2004.
Download Database and Analysis Programs
The data and software used to produce the individual frames and
animation at the top of the page may be downloaded from the
following links. The population and IQ data are extracted from
the Global Composite Country Database in CSV (Comma-Separated
Value) format, which contains a variety of other data assembled
from resources on the Web. CSV files can be loaded into most
spreadsheet and database programs. Lines which begin with a
sharp sign (“#”) are comments—if your software
doesn't ignore them, you should manually delete them before or
after loading the database. The first non-comment record gives
the field names in the data which follow. The contents of the
fields and the sources from which they were obtained is given
in the following comments. Fields for which no data are
available or are inapplicable are left blank.
The analysis and image generation was performed by a purpose-built
program which you can download from the second link below.
This program contains little or no documentation
and is utterly unsupported—you are entirely on your own.
Histograms are plotted with the
package and post-processed with utilities from the
image processing toolkit. The animation was assembled with the
utility. These are all free software which may be downloaded from the
by John Walker