height has commonly been attributed to social processes, in which taller individuals are treated differently than shorter ones. For instance, a common theory in social psy-
chology postulates that taller people are more successful for reasons of interpersonal dominance. See, for example, Frieze, Olson, and Good 1990. It then follows that if
being tall is an advantage in different competitive situations, this may facilitate the building of self- esteem and social skills in relatively taller individuals. Moreover,
children may face different expectations from parents, teachers, other adults, and peers depending on their height. If children react to expectations by complying, such
expectations may become self- fulfi lling. For instance, if taller children are perceived and treated as being more mature, when it comes to temperance, responsibility, and
planning, they may well be fostered into developing such traits.
As discussed by Persico, Postlewaite, and Silverman 2004, another explanation emphasizes the role of self- esteem, but from a different perspective. Here, the height
premium stems from the greater self- image that is achieved through a comparison with a socially determined notion of ideal height. It is then argued that a greater self-
image leads to higher achievement through noncognitive factors such as perseverance and social skills. This is related to the fi ndings of Persico, Postlewaite, and Silver-
man 2004, where teen height is found to explain a large part of the relationship between height and earnings, and where the premium is reduced when controlling
for participation in high school sports and clubs. The latter fi nding causes the authors to conclude that such participation shapes noncognitive skills. This is well in line with
Kuhn and Weinberger 2005 who, controlling for cognitive ability, found that self- perceived leadership skills as well as exposure to leadership positions in high school,
was positively related to earnings later in life. Moreover, Lindqvist 2012 fi nds that height is positively related to leadership skills, as measured at the Swedish enlistment.
In sum, existing explanations for the association between height and noncognitive skills in general focus on how height may affect the development of noncognitive
skills, rather than both being determined by some third, underlying factor. From these respects, noncognitive skill is a mediating factor in explaining the height premium.
7
C. Muscular Strength
It has long been known that anthropometric measures such as body height are strongly correlated with muscular strength. See Everett and Sills 1952 for an early example.
If muscle strength would also have an independent infl uence on earnings, part of the height- earnings relationship would refl ect the association between height and muscle
strength. Though admittedly, the direct importance of muscle strength for labor market success has likely declined with the development of society and modern production
7. While we believe that available evidence points to the view that height does affect the development of noncognitive skills, we note that there may be important underlying factors governing both as well. As
argued by Schick and Steckel 2010 important dimensions of noncognitive skill concern the ability to make judgment based on experience in favor of pure instinct for example, to forego immediate returns in favor of
future ones. Similarly to cognitive ability, this kind of ability increases with age in childhood and youth as the brain develops. Given that both cognitive and noncognitive skills are based on mental processes, it seems
logical that nutritional infl uences may affect not only height and cognitive ability but via neural growth also the development of noncognitive skill. Insofar the association between height and noncognitive ability also
is due to a third underlying factor that is, nutrition, one cannot rule out that parts of this type of skill should be regarded as a control variable when estimating the correlation between height and earnings.
processes, there are still a number of reasons why it may be correlated with labor market success in the western world.
First, the development of the muscular system may be related to the same ge- netic predispositions and susceptible to the same environmental conditions as height
growth, thereby yielding a positive correlation between the two Silventoinen et al. 2008.
8
To the extent that the same genetic and environment factors also infl uence a person’s labor market success, muscle strength would be an important control variable
when estimating the height premium. A second possibility is that tall people to a larger extent participate in activities that
not only builds noncognitive skills, as suggested by Persico, Postlewaite, and Silver- man 2004, but also muscle strength, such as sports, and that these same characteris-
tics have a labor market return. See Rooth 2011. In fact, to the extent that being tall constitutes an advantage in certain sports activities, one would expect tall people to
participate to a greater extent. From this perspective, muscle strength would instead be a mediating factor in the height- earnings relationship, because it may partly be
caused by being tall.
Finally, it is also possible that male muscle strength signals certain personality traits. Some studies have for instance found that handgrip strength predicts not only
physical fi tness but also aggressiveness and dominance Gallup, White, and Gallup 2007. These traits can be recognized as dimensions of noncognitive skills, which
would mean that muscle strength would partly pick up the same factors as direct mea- sures of noncognitive skills.
Even though there are good reasons to believe that muscle strength may play a role in the height- earnings relationship, our discussion also shows there is great uncer-
tainty about the mechanisms at work. In our empirical analysis, we will therefore be somewhat agnostic about whether muscle strength mainly plays the role of a control
variable or a mediating variable and leave that for future research to investigate.
D. Empirical Framework
