Question
Why are IQ tests renormed?
Short answer
IQ tests are renormed because average performance drifts over time. Measured IQ rose about 3 points per decade in US data through the 20th century, so a test scored against old norms would put today’s average person above 100. New norms, built from a fresh sample, reset the average to 100 and keep scores meaningful.
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What norms are
An IQ is a comparison. Test makers give the test to a large standardization sample at each age, and your score shows where you fall relative to that sample, on a scale with mean 100 and standard deviation 15 (Wikipedia: Intelligence quotient). Those sample results are the test's norms. See the glossary entry for standardization sample.
Why norms go out of date
Average measured IQ rose through the 20th century. Flynn documented about 3 points per decade in the US, and a 2015 meta-analysis of 271 samples, about 4 million people across 31 countries, estimated about 2.8 points per decade, with the gains slowing in recent decades (Pietschnig & Voracek, 2015). This is the Flynn effect.
If a test kept norms from decades earlier, today's typical person would beat the old average and score well above 100. The score would be inflated by the age of the norms, not by anything about the person.
Try one · Abstract Reasoning
Which tile completes the grid?
Tap the option you think is right, or show the answer.
Show the answer
The missing tile has two solid triangles (option 4).
How to solve it
- Start with the first row and name what changes from tile to tile.
- Every row and every column contains each shape (star, triangle and square) exactly once.
- Every row and every column contains each number of shapes (two, three and one) exactly once.
- The fill (solid) stays the same in every tile.
- Check the rules on the second row, then apply them to the third.
- So the missing tile has two solid triangles.
That was 1 puzzle. The full test has 25.
Drift goes both ways
A reversal, sometimes called the negative Flynn effect, has been reported in Norwegian conscript data for cohorts born after about 1975 (Bratsberg & Rogeberg, 2018). Renorming corrects for that too. The goal is the same either way: 100 should mean average for the people taking the test now.
How it shows up
New editions are one place renorming appears. The Wechsler adult scale moved from WAIS-IV in 2008 to WAIS-5 in 2024 (Wikipedia: WAIS). When comparing scores, it helps to know which edition, and so which norms, produced them. Read the Flynn effect for the research, or why the average IQ is 100 for how the scale is set.
Sources
- Pietschnig, J., & Voracek, M. (2015). One century of global IQ gains. Perspectives on Psychological Science, 10(3), 282-306. doi.org/10.1177/1745691615577701
- Bratsberg, B., & Rogeberg, O. (2018). Proceedings of the National Academy of Sciences, 115(26), 6674-6678. doi.org/10.1073/pnas.1718793115
- Wechsler Adult Intelligence Scale. Wikipedia. en.wikipedia.org/wiki/Wechsler_Adult_Intelligence_Scale
- Intelligence quotient. Wikipedia. en.wikipedia.org/wiki/Intelligence_quotient