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Global IQ: 1950–2050

Essentially the idea is that while smart people are getting wealthier, their birth-rate tends to drop. On the other hand poor countries, which are generally populated by less intelligent people, have constant birth rates.

So theoretically this would lead in drops of the global IQ, as the global population is rising. Is this true?

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    Just to complicate matters you'll note in the answers that there is some question about how well IQ tracks the (assumed to exist) underling "G" or "general intelligence".
    – dmckee --- ex-moderator kitten
    Commented Feb 29, 2012 at 20:45
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    This theory is the basis of the Mike Judge film Idiocracy, in which a couple of modern average-Joes get transported 500 years into the future, to find they are now the smartest people alive. Sadly, not one of his better works, but still funny.
    – Flimzy
    Commented Feb 29, 2012 at 21:43
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    It also is the premise of the classic SF story "The Marching Morons" in which the problem is "solved" by enticing all the morons to emigrate to Venus, where they die.
    – Larry OBrien
    Commented Mar 1, 2012 at 1:35
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    Average IQ is a weighed average over a population at a point in time. By definition it will always be 100 on average. So no, IQ is constant over time. The test results candidates would get out of tests specified at particular times and places may of course change (in fact are expected to as tests are modified for cultural and societal changes).
    – jwenting
    Commented Mar 1, 2012 at 6:51
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    Your assumption is, that less intelligent people are so by genetic disposition, not by the circumstances. If you assume a childless teacher increasing the intelligence of his pupils, it might work the other way round.
    – user unknown
    Commented Mar 2, 2012 at 15:21

3 Answers 3

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N.B. IQ scores are standardized for a given population at a given time. The average IQ is always 100, and its standard deviation is always 15. To compare between times or populations, we must use “raw IQ,” by which I mean the raw scores of a few tests, especially:

  • Raven's Matrices, a test of pattern recognition
  • Digit span, a test of short-term memory

It's been discussed before whether such tests measure intelligence, and whether intelligence even exists. But if intelligence does exist, and it increases generation-by-generation as children receive better care and nutrition, then Raven's and digit span are particularly good tests for showing that increase.

The Flynn effect is a very well-known phenomenon by which the raw IQ of a population increases over time. It's been specifically studied in rural Kenya, where the paper's authors found that – mainly due to smaller families, better nutrition, and an increased literacy rate among parents – the raw IQ of Kenyan children is increasing, at a rate comparable to that in industrialized nations. As the birth rate decreases and nutrition and literacy improve, that rate will increase. As it rises above the rate in industrialized nations, the "IQ gap" will disappear.

The site you link to ignores the Flynn effect entirely. It takes average raw IQ scores from a few dozen nations, estimates the rest based on “demographic mix,” and then assumes that each nation won't change in intelligence, even for 100 years (despite Flynn's studies having proved an increase). The site hand-waves this, saying that the Flynn effect is “undisputed yet enigmatic” and then arguing that it doesn't exist, since:

  • It would imply that people in the past were far less intelligent than the current standard, yet “the literature and music of a century or more ago is clearly not the work of marginally retarded minds.”
  • Most parents think their children are dumber than they are.

The second isn't worth responding to. The first fundamentally misunderstands the Flynn effect. Let's compare the increase in intelligence to the (better documented) rise in life expectancy. Life expectancy at birth remained at about 30 years for 50 000 years of human history, then skyrocketed at industrialization. The overall trend isn't people have lived progressively longer throughout history, but rather there has been a dramatic increase in life expectancy tied to industrialization. It's also worth noting that as the average life expectancy rose, the distribution changed as well, since most of the change is due to lower infant mortality. Just as today, some people in medieval and ancient times lived to be 90. Similarly, the Flynn effect doesn't imply that people have gotten more intelligent throughout history, nor that there weren't any geniuses in the past.

Clearly, intelligence in industrializing nations is growing along with that of industrialized nations. As their HDI increases, the rate of intelligence growth will increase as well. So not only is the world getting smarter, but also currently industrializing nations will produce the greatest future gains in aggregate intelligence.

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    A small caveat. The Flynn effect shows an increase in IQ over times, which although related is not the same thing as Intelligence. I don't think your answer should talk about a rise in intelligence, but instead be restricted to IQ.
    – Sonny Ordell
    Commented Mar 1, 2012 at 1:52
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    @Sonny I wanted to avoid saying "increase in IQ," since IQ is by definition standardized at 100 for a given population. What I really mean here is that the Kenyan children's raw scores for Raven's Matrices, the Verbal Meaning Test, and a digit span test all increased generation-by-generation. Raven's Matrices rose the most, and it's a good measure of fluid intelligence, especially in those who haven't seen the test before.
    – Chel
    Commented Mar 1, 2012 at 11:53
  • In that case I would suggest incorporating that into your answer, just because I think it is more accurate and the term intelligence can be troublesome. It has been a point of contention for some questions on the site previously.
    – Sonny Ordell
    Commented Mar 1, 2012 at 12:13
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    I tend to think about IQ scores as an inverse measure of deprivation. I believe that if people get some basic nutrition and education, intellectual capacity will flourish, and additional efforts to boost IQ scores will be futile. Deprivation, on the other hand, can harm intellectual capacity in many ways. In that sense, industrialization would act to suppress sources of deprivation, and the previously deprived portions of the population would flourish with the rest of us. And industrialization will come everywhere - it's no coincidence that we call poor countries 'developing'.
    – Ana
    Commented Mar 3, 2012 at 9:49
  • James Flynn's TED talk on improving education and his understanding of the effect.
    – lly
    Commented Jul 22, 2018 at 11:55
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Just the opposite.

The Flynn Effect observes that global IQ scores are actually increasing over time at a pretty good clip. The true extent and cause of the effect are a matter of debate (but the effect is more pronounced at the low end of the spectrum, so the theory that increased nutrition and healthcare are a "rising tide that floats all boats" is appealing).

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Changes in relative numbers of high-intelligent and low-intelligent people in the world should never lead to a change in global IQ.

IQ is not a measure of amount of intelligence, it is a measure of amount of intelligence relative to peers.

For example, see this source:

And it is very important for people not to confuse between intelligence and relative intelligence. Intelligence can never be measured and IQ is not the measure of intelligence. IQ is simply the measure of relative intelligence derived by a single or set of standardized tests.

For example, a young child can have a higher IQ than an adult, even though the adult has plenty more intellectual capacity, because, the peers of a child are not the same as the peers of an adult:

Modern IQ tests use a "deviation IQ" rather than a ratio IQ. With this method, test takers are referenced to other people of their own age. The average IQ is still 100, but deviations from the average are assigned a number which corresponds to a percentile rank.

Esentially, IQ is a measure of ranking, not of amount of ability. The rankings are expressed in IQ points, which are usually equal to 1/15th of a standard deviation of all possible test-takers.

There are standards for assigning IQs to people who get a certain number of questions correctly. These standards change over time, so that the average is always 100:

Because populations experience IQ gains over time, IQ tests must be constantly restandardized so that subjects are not scored against inaccurate norms.

That being said, the standards are not updated all the time, and certainly not in all countries. What Lynn and Vanhanen do, in the study that inspired your question, is to give a test that has been standardized in the Western world, to nationals of many countries across the globe.

Norms: Norm groups included in the manual are: British children between the ages of 6 and 16; Irish children between the ages of 6 and 12; military and civilian subjects between the ages of 20 and 65. A supplement includes norms from Canada, the United States, and Germany.

This is the standard that all other people are compared to, when assessing their ranking on the IQ scale.

If the tests were always standardized correctly, that is to (a representative sample of) all potential test-takers, the average global IQ would be 100 every time it is measured. So, no, global IQ should never drop.

But perhaps it does drop? It is, after all, a highly imperfect set of numbers. If global IQ were to drop, we could speculate on the reasons. One of the reasons could be that a putative gap in intelligence between more and less developed countries is widening. This means that the Western standards for assigning IQ points get tougher and tougher for poor, more populous countries. Note that this still doesn't need to mean that global levels of intelligence are dropping! All countries could do better nowadays, but the gap might still widen. Following the pattern of IQ scores over time simply doesn't tell us what is happening with the actual level of intelligence.

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