Educability-and-Group-Differences-1973-by-Arthur-Robert-Jensen

160 Educability and Group Differences
attenuated by intrinsically irrelevant racial characteristics such as
skin color. These irrelevant characteristics may operate negatively
or positively (i.e., as hindrances or advantages in upward socioeconomic
mobility) to weaken the correlation between ability and
SES. If there were no racial discrimination of any kind, SES
differences would be determined equally by ability in all racial
groups. SES differences among races would then be merely an
incidental correlate of ability differences among racial groups. Since
this has surely not been the case, we can place much less confidence
in SES as an index of genetic ability differences between racial
groups than within groups. And we can also place less confidence
in the meaning of SES differences within those racial groups for
whom variations in irrelevant physical characteristics such as skin
color may also play a part in social mobility. As all forms of racial
discrimination diminish, we can expect SES increasingly to reflect
the same ability and personality traits between as well as within
racial groups. It has been pointed out by Duncan (1969) that in
1964,
. . . the earnings of Negro men aged 25 to 34 were about 55
percent as great as those of white men of the same age. The
dollar gap amounted to some $3,000. Eighteen percent of this
gap could be attributed to the disadvantageous social origins of
Negro men, indexed by the educational and occupational levels
of the heads of families in which they grew up. An additional
3 percent was due to the racial differential in size of families of
orientation. Some 22 percent of the gap not already accounted
for arose from differences in the realized mental abilities of
white and Negro children, as revealed in standard tests. Apart
from differences in family size and socioeconomic level, and
apart from differences in mental test scores, length of schooling
accounted for 2 percent of the income differential. Another 12
percent turned on the differences between white and Negro
men in the occupations followed, excluding factors of education,
mental ability, number of siblings, and social origins. Altogether,
the calculation accounts for some four-sevenths of the income
gap. The remaining three-sevenths (43 percent) is due to the
fact that Negro men in the same kinds of occupations, with the
same amount of schooling, with equal mental ability, having
come from families of the same size and socioeconomic position,