>Not the judgment of the "average" person, but the averaged judgments of many persons can show an extraordinary consistency across quite diverse groups of persons, and from one generation to the next, as well as remarkably high correlations with certain independent objective criteria. Such is the case with people's average subjective judgments of occupational "level" and their high correlation with the average tested IQs of persons in various occupations. The striking finding has been demonstrated to about the same high degree in numerous studies and has been contradicted by none.
People's average ranking of occupations is much the same regardless of the basis on which they were told to rank them. The well-known Barr scale of occupations was constructed by asking 30 "psychological judges" to rate 120 specific occupations, each definitely and concretely described, on a scale going from 0 to 100 according to the level of general intelligence required for ordinary success in the occupation. These judgments were made in 1920. Forty-four years later, in 1964, the National Opinion Research Center (NORC), in a large public opinion poll, asked many people to rate a large number of specific occupations in terms of their subjective opinion of the prestige of each occupation relative to all of the others. The correlation between the 1920 Barr ratings based on the average subjectively estimated intelligence requirements of the various occupations and the 1964 NORC ratings based on the average subjective opined prestige of the occupation is .91. The 1960 U.S. Census of Population: Classified Index of Occupations and Industries assigns each of several hundred occupations a composite index score based on the average income and educational level prevailing in the occupation. This index correlates .81 with the Barr subjective intelligence ratings and .90 with the NORC prestige ratings.
Rankings of the prestige of 25 occupations made by 450 high school and college students in 1946 showed the remarkable correlation of .97 with the rankings of the same occupations made by students in 1925 (Tyler, 1965). Then, in 1949, the average rankings of these occupations by 500 teachers college students correlated .98 with the 1946 rankings by a different group of high school and college students. Very similar prestige rankings are also found in Britain and show a high degree of consistency across such groups as adolescents and adults, men and women, old and young, and upper and lower social classes. Obviously people are in considerable agreement in their subjective perceptions of numerous occupations, perceptions based on some kind of amalgam of the prestige image and supposed intellectual requirements of occupations, and these are highly related to such objective indices as the typical educational level and average income of the occupation. The subjective desirability of various occupations is also a part of the picture, as indicated by relative frequencies of various occupational choices made by high school students. These frequencies show scant correspondence to the actual frequencies in various occupations; high-status occupations are greatly overselected and low-status occupations are seldom selectes.
How well do such ratings of occupations correlate with the actual IQs of the persons in the rated occupations? The answer depends on wether we correlate the occupational prestige ratings with the average IQs in the various occupations or with the IQs of individual persons. The correlations between average prestige ratings and average IQs in occupations are very high - .90 to .95 -when the averages are based on a large number of raters and a wide range of rated occupations. This means that the average of many people's subjective perceptions conforms closely to an objective criterion, namely, tested IQ. Occupations with the highest status ratings are the learned professions - physician, scientist, lawyer, accountant, engineer, and other occupations that involve high educational requirements and highly developed skills, usually of an intellectual nature. The lowest-rated occupations are unskilled manual labor that almost any able-bodied person could do with very little or no prior training or experience and that involves minimal responsibility for decision or supervision.
The correlation between rated occupational status and individual IQs ranges from about .50 to .70 in various studies. The results of such studies are much the same in Britain, the Netherlands, and the Soviet Union as in the United States, where the results are about the same for white and blacks. The size of the correlation, which varies among different samples, seems to depend mostly on the age of the persons whose IQs are correlated with occupational status. IQ and occupational status are correlated .50 to .60 for young men ages 18 to 26 and about .70 for men over 40. A few years can make a big difference in these correlations. The younger men, of course, have not all yet attained their top career potential, and some of the highest-prestige occupations are not even represented in younger age groups. Judges, professors, business executives, college presidents, and the like are missing occupational categories in the studies based on young men, such as those drafted into the armed forces (e.g., the classic study of Harrell & Harrell, 1945).
Evidence contradicts the notion that IQ differences between occupations are the result rather than a cause of the occupational difference. Professional occupations do not score higher than unskilled laborers on IQ tests because the professionals have had more education or have learned more of the test's content in the pursuit of their occupations. A classic study (Ball, 1938) showed that childhood IQs of 219 men correlated substantially with adult occupational status as measured on the Barr scale some 14 to 19 years later - a correlation of .47 for a younger sample of men and of .71 for a sample of older men just five years further into the careers. ...<
Arthur Jensen; 1980
Bias in Mental Testing