Average IQ by Occupation: What the 1940s Army Data Shows
Nearly every "IQ by profession" chart online traces to one 1945 study of wartime enlisted men, scored on a scale that modern IQ tests do not use. Here is what that table shows and what still holds up.
What you need to know
- Average IQ by occupation figures come from 1940s Army data, not a current survey. Nearly every chart traces to Harrell and Harrell's 1945 study of 18,782 enlisted men, scored on the Army General Classification Test (AGCT).
- The AGCT was scored on a mean-100, standard-deviation-20 scale, not the mean-100, standard-deviation-15 scale modern deviation IQ tests use, so a raw AGCT score of 128 does not sit at the same percentile a modern IQ score of 128 does.
- In the table as widely reproduced, accountants topped the list at a mean of 128.1 and teamsters sat lowest at 87.7. We could not open the 1945 paper's table to check each figure, and the numbers are 80 years old, so the ranking is a pattern to note and not a score to quote.
- Modern research finds that general mental ability predicts occupational level and job performance (Schmidt and Hunter, 2004), but estimates of the link to job performance have fallen from .51 (1998) to about .31 (Sackett and colleagues, 2022), so a chart of exact scores by job title is not the finding worth taking.
If you have seen a chart online ranking IQ by job — accountants and lawyers near 128, teachers in the low 120s, unskilled trades down in the 90s or below — you have seen a repackaging of one specific dataset from 1945, almost never credited to its source.
Where does average IQ by occupation come from?
The original source is a 1945 paper by Thomas W. Harrell and Margaret S. Harrell, "Army General Classification Test Scores for Civilian Occupations", in Educational and Psychological Measurement (volume 5, pages 229 to 239). It analysed Army General Classification Test (AGCT) scores for 18,782 enlisted men in the Army Air Force Command. The men were grouped by the civilian occupation each had held before enlisting. It is a wartime sample of one branch and one sex, tested on a 1940s military instrument.
We could not open the paper's table. The figures below are as reproduced in later sources and are not checked against the original, so the pattern matters more than any third digit. N. Stewart's 1947 paper in Occupations also grouped AGCT scores of Army personnel by occupation.
Which jobs have the highest average IQ?
Which jobs have the highest average IQ? In the 1945 Army table as widely reproduced, accountants score highest (mean 128.1), followed by lawyers (127.6), engineers (126.6), auditors (125.9) and chemists (124.8). Teamsters (87.7), miners (90.6) and farmers (92.7) have the lowest means among the 20 occupations printed below. These are AGCT scores on a scale with a standard deviation of 20. So the accountants' 128.1 is about 121 on the usual SD-15 scale (our arithmetic: 1.4 standard deviations above 100). The scores describe wartime enlisted men, not today's workers, and we found no current survey that replaces them.
What does the 1945 occupation table show?
A representative slice of the table, as reproduced in later sources, with each occupation's mean AGCT score:
- Accountant: 128.1
- Lawyer: 127.6
- Engineer: 126.6
- Auditor: 125.9
- Chemist: 124.8
- Teacher: 122.8
- Draftsman: 122.0
- Bookkeeper: 120.0
- Purchasing agent: 118.7
- Clerk, general: 117.5
- Salesman: 115.1
- Manager, retail store: 114.0
- Machinist: 110.1
- Electrician: 109.0
- Auto mechanic: 101.3
- Carpenter, construction: 102.1
- Farmer: 92.7
- Laborer: 95.8
- Miner: 90.6
- Teamster: 87.7
Why is the scale a problem?
The AGCT was normed to a mean of 100 with a standard deviation of 20, not the mean-100, standard-deviation-15 scale that modern deviation IQ tests use. That difference matters arithmetically, not just historically. A score of 128 on the AGCT’s SD-20 scale sits 1.4 standard deviations above the mean, which our own percentile calculator places at roughly the 92nd percentile. Treat that same "128" as if it came from a modern SD-15 IQ test instead, and it implies 1.87 standard deviations above the mean — close to the 97th percentile. Same number, two different rarity claims, depending on a scale nobody printed on the chart. The lawyer figure is the best-known case: our guide to the average IQ of lawyers converts the 127.6 and sets out what the LSAT and the bar exam do publish.
The number on a viral "IQ by profession" chart is usually real. The scale it was measured on almost never survives the trip from a 1945 journal table to a social media post — and the scale is the part that decides what the number actually means.
What holds up in modern research, and what does not?
The specific 1945 numbers should not be quoted as a current fact about any occupation today. What has held up is the broader pattern. Schmidt and Hunter's 2004 review in the Journal of Personality and Social Psychology presents evidence that general mental ability predicts the occupational level people reach and their performance within an occupation. It says these relationships are larger than most found in psychological research.
The size of the link to job performance is debated. Schmidt and Hunter's 1998 estimate was .51. A 2022 re-analysis by Sackett and colleagues put it at about .31.
How much does ability matter in different jobs?
Schmidt and Hunter's 1998 review reported that the link between general mental ability and job performance grows with a job's complexity:
- Professional and managerial jobs: .58
- High-level complex technical jobs: .56
- Medium-complexity jobs: .51
Do hiring tests use the same idea today?
Cognitive tests have been used in hiring for generations. A current example is the Wonderlic cognitive test, with 50 questions and a 12-minute limit, as Wonderlic states. Our piece on converting a Wonderlic score to an IQ estimate covers that test. Our guide to Wonderlic scores by job explains why the numbers quoted for each job come from an older version of the test. The scale caution that applies to the 1945 AGCT table applies there too, because the Wonderlic has its own scale. For the military's own screen, see our guide to ASVAB and AFQT scores, which explains why there is no official conversion to IQ.
Why can a chart like this not simply be updated?
We found no modern dataset that scores a nationally representative population on one standardized test and records detailed occupation alongside it the way the wartime Army data did. Related, narrower pictures exist on this site: our pieces on whether IQ predicts income and on average IQ by education level cover adjacent modern data using the same kind of large-sample research this occupational question would need. Single occupations that have their own selection tests are covered one by one: see the average IQ of software engineers, where no study measured it, and the smartest NBA players, where the Combine's cognitive test gives no IQ numbers. Until an equivalent dataset exists for occupation specifically, the honest version of this chart is the general finding — ability tracks occupational level and job performance — not a specific score next to a specific job title. Two flying jobs are examined in our guide to the average IQ of pilots and air traffic controllers.
Where would your own score land?
Rather than trust an 80-year-old number, see where your own score actually sits. Take the full IQ assessment or run a score through our percentile calculator for a result anchored to a real, current reference population.
Find your IQ score now! →The next time that chart resurfaces, the two facts worth adding are the ones it always leaves out: the data is from 1945, and the scale it used is not the one being assumed when someone reads it today. If you want a score anchored to the present rather than to a wartime draft roster, our IQ test reports one, with the percentile attached. For doctors there is no reliable figure either; see MCAT score to IQ. Hiring teams that want a structured, current measure can read about cognitive assessment for hiring teams.
Common questions
Where do average IQ by occupation charts come from?
Almost all trace back to Harrell and Harrell's 1945 study of Army General Classification Test scores for 18,782 enlisted men in the Army Air Force Command, grouped by their pre-enlistment civilian occupation.
Which jobs have the highest average IQ?
In the 1945 Army data as widely reproduced, accountants (mean 128.1), lawyers (127.6), engineers (126.6), auditors (125.9) and chemists (124.8) scored highest on the AGCT. That scale has a standard deviation of 20, so 128.1 is about 121 on the usual SD-15 scale, and the data are 80 years old.
Is there a current average IQ by occupation?
We found no current survey that measures it. Pages that claim one usually repeat the 1945 Army table, and questions about single occupations such as lawyers, software engineers and NBA players have no measured average IQ either.
Is the Army General Classification Test the same scale as a modern IQ test?
No. The AGCT was normed to a mean of 100 with a standard deviation of 20. Modern deviation IQ tests use a mean of 100 with a standard deviation of 15, so identical numbers on the two scales correspond to different percentiles.
Does modern research still find a link between cognitive ability and occupation?
Yes. Schmidt and Hunter (2004) review evidence that general mental ability predicts the occupational level people reach and their job performance. The size of the link to job performance is debated: .51 in a 1998 review and about .31 in a 2022 re-analysis.
Sources for this story
- Army General Classification Test scores for civilian occupations (1945), Educational and Psychological Measurement, 5(3), 229-239 — Harrell, T. W., & Harrell, M. S.
- AGCT scores of Army personnel grouped by occupation (1947) — Stewart, N., Occupations: The Vocational Guidance Journal
- General Mental Ability in the World of Work: Occupational Attainment and Job Performance (2004) — Schmidt, F. L., & Hunter, J. E., Journal of Personality and Social Psychology
- The validity and utility of selection methods in personnel psychology: Practical and theoretical implications of 85 years of research findings (1998) — Schmidt, F. L., & Hunter, J. E., Psychological Bulletin
- Revisiting meta-analytic estimates of validity in personnel selection: Addressing systematic overcorrection for restriction of range (2022) — Sackett, P. R., Zhang, C., Berry, C. M., & Lievens, F., Journal of Applied Psychology
Corrections: spotted an error? Email corrections@iqmetrics.org and we will update this story and note the change here.
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