“IQ” stands for “intelligence quotient.” A person’s IQ is a score derived from standardized tests that were designed to measure human intelligence and intellectual potential. IQ tests include a variety of questions that measure reasoning and problem-solving skills.

IQ scores are often used for placement in educational or school programs or to evaluate someone for mental disabilities. IQ tests are also sometimes used as part of a job application.

Research has discovered that average IQ differs around the globe. The reason for this disparity has been of great interest to scientists for quite some time. It’s also been a major source of controversy.

The debate centers on whether these differences in IQ are caused by genetics, environmental factors, or both. This is why understanding what average IQ means, and doesn’t mean, is incredibly important.

What is the average IQ globally and in the United States?

IQ tests are made to have an average score of 100. Psychologists revise the test every few years in order to maintain 100 as the average. Most people (about 68 percent) have an IQ between 85 and 115. Only a small fraction of people have a very low IQ (below 70) or a very high IQ (above 130).

The average IQ in the United States is 98.

Over the years several researchers, including Lynn and Vanhanen (2002), Rinderman (2007), and Lynn and Meisenberg (2010), tried to figure out how each country ranks in terms of IQ.

According to the results of Lynn and Meisenberg’s research, for example, out of 108 countries and provinces, the United States ranks 24th in IQ globally (tied with Australia, Czech Republic, Denmark, France, Latvia, and Spain) with an average IQ of 98. The top 10 countries by average IQ are:

1. Hong Kong (108)

2. Singapore (108)

3. South Korea (106)

4. China (105)

5. Japan (105)

6. Taiwan (105)

7. Iceland (101)

8. Macau (101)

9. Switzerland (101)

10. Austria (as well as Liechtenstein, Luxembourg, Netherlands, Norway, UK) (100)

According to the same study, the bottom 10 countries by average IQ are:

93. Kenya (as well as Namibia, South Africa, Tanzania) (72)

94. Zimbabwe (72)

95. Botswana (71)

96. Ghana (71)

97. Zambia (71)

98. Nigeria (69)

99. Swaziland (68)

100. Lesotho (67)

101. Mozambique (64)

102. Malawi (60)

The studies used to support these data, however, are controversial. This is in part because they may have considered only specific population groups or a small sample size per country.

How is IQ measured?

Modern IQ testing in the United States comes from the work of psychologist Henry Herbert Goddard. Goddard helped translate an intelligence test developed by French psychologist Alfred Binet to English.

This test was used by Binet to evaluate basic intellectual functions in school children and to assist with mental health diagnoses. IQ tests have evolved considerably since then. Today, there are more than a dozen different tests used to measure intelligence.

In general, an IQ test is used to evaluate a person’s reasoning and problem-solving skills. Some of the most widely used IQ tests include:

  • Wechsler Intelligence Scale for Children (WISC-V)
  • Wechsler Intelligence Scale for Adults (WAIS)
  • Stanford-Binet Intelligence Scale
  • Differential Ability Scales (DAS)
  • Peabody Individual Achievement Test

The tests are given by licensed psychologists. They are usually composed of several parts. The Wechsler Intelligence Scale, for example, contains 15 subtests.

Each subtest measures a different aspect of IQ, such as math, language, reasoning, memory, and information-processing speed. The results are then combined into one score called the IQ. The scores are also adjusted by age.

Rising IQs

Since the early 1900s, raw scores on IQ tests have largely increased in most parts of the world. This phenomenon is sometimes called the “Flynn effect” after the scientist who discovered it, James Flynn.

In the 1980s, Flynn noticed that U.S. military personnel who took IQ tests in the 1980s did much better than those who took the same test in the 1950s. After doing more research, Flynn discovered that IQ scores had been rising all over the world by about three points or more per decade.

Then again, we haven’t necessarily gotten smarter or more evolved than our ancestors.

Scientists believe this increase in IQ is because we’ve improved our abilities to think logically, solve problems, and consider hypothetical situations. It’s also likely due to an increase in formal education, vaccinations, and better nutrition.

Why the test is controversial

Average IQ has been a controversial subject ever since intelligence tests were invented.

Some people erroneously believe that people of certain races, sexes, or backgrounds have lower IQs due to their genes and that they are therefore inferior. This information has been used to fuel racist agendas and eugenics movements around the globe.

While a number of individual genes have been reported to be associated with IQ, none have been shown to have a strong effect. The American Psychological Association also hasn’t found evidence to support genetic explanations for IQ score differences between different races.

Studies also haven’t been able to find a difference in average IQ scores between men and women.

It’s also important to remember that the concept of IQ and IQ tests were developed by western Europeans according to their own cultural standards. It’s still unclear whether IQ can accurately measure intelligence in people with completely different social structures, cultures, beliefs, and ways of thinking.

On top of this, it’s clear that environmental factors play a huge role in average IQ. Factors that have been positively associated with higher IQ include:

  • good nutrition
  • regular schooling of good quality
  • laws requiring fortification of certain food products
  • laws establishing safe levels of pollutants, like lead
  • musical training in childhood
  • higher socioeconomic status
  • lower incidence of infectious diseases

A recent study found that infectious disease may be the only really important predictor of average IQ. Researchers believe that this is because if a child becomes ill, the body uses its energy to fight off the infection rather than using it for brain development.

One study found that cognitive abilities and school performance were impaired in people with malaria (an infectious disease spread by mosquitos) compared to healthy controls.

A study done in the United States found a strong correlation between states with a higher incidence of infectious diseases and lower IQ.

IQ isn’t the only way to measure intelligence

The average IQ is widely used to measure human intelligence and is a useful tool. However, it comes with many caveats. Average IQ varies by country, and some people have manipulated this information to justify racist motives.

However, environmental factors, like access to education and proper nutrition as well as the incidence of infectious diseases, have been shown to play a bigger part in explaining the difference in IQ from country to country.

An IQ score probably doesn’t tell the whole story. While IQ scores can give us important insights into intelligence, it may fail to measure broader definitions of intellect, like creativity, curiosity, and social intelligence.

So, don’t worry if you’re not considered a genius by your IQ test results — the vast majority of people aren’t. There are many other factors that determine your success.