In honor of #Star Wars Day (May the Fourth be with you. Always), let’s revisit one of the classic lines from the original trilogy: Aren’t you a little short for a Stormtrooper?
Well, maybe Luke was a little short. But that’s beside the point – should the Empire have been selecting Stormtroopers on the basis of height?
Unfortunately, due to the fact that this personnel selection problem existed a long time ago in a galaxy far, far away, we can’t comment on the Empire’s hiring practices and how they conformed to rule of law. However, what does the relationship of height to job success look like today?
Height and Performance
There is some research suggesting a relationship between height and job performance(1) in that taller people tend to perform better than shorter people. This relationship holds for samples of men only, women only, and mixed samples. (Why this relationship exists is not well understood, but we’re focusing on the simple fact that is does exist.)
Additionally, this relationship is particularly strong for sales positions(1) – there is a substantial relationship between height and sales income, where taller salespeople earn more money.
Now suppose we’re hiring for a sales position. Does this mean we should use height as a job requirement?
#Adverse Impact
The answer, of course, is NO!
But let’s unpack this a little bit – why would it be a bad decision to select on height?
It’s common knowledge that, on average, men are taller than women. According to the CDC(2) (no, that's not a Star Wars character), the average height is 69.2 inches (just over 5’9”) for men and 63.7 inches (just under 5’4”) for women. If height were instituted as a job requirement, it’s clear that many more men would be selected than women. For example, if a cutoff value for height were instituted such that 50% of men moved on in the selection process, only about 18% of women would move on(3). When selection rates are this different, it’s called Adverse Impact, and it can pose a huge risk for employers. (Similar patterns of adverse impact also occur against Asian and Hispanic applicants, in addition to women.)
When adverse impact against a protected group occurs, the employer has the burden of proof to demonstrate that the selection practice (in this case, height) is job-related. We noted above that height is related to sales income, so is that enough?
Again, no. The employer also has the burden to show that no reasonable alternative exists that would yield less adverse impact. Good luck with that! Looking at ONET’s detailed job analysis information for sales representatives, there is exactly zero mention of height as a job requirement, nor any data suggesting height is important to success on the job. But there are plenty of alternatives with direct links to job performance (e.g., sales and marketing knowledge, dependability, oral and written comprehension).
Protecting Yourself
You may be asking yourself how you can avoid the legal risk associated with adverse impact in your hiring practices. Here are a couple tips:
Keep it job-related. When setting up your job and your selection system, make sure all your requirements are job-related. The default selections in career.place for hard skills and assessments are based on ONET’s job-analysis information, which helps ensure that these selections are linked back to the requirements of the job.
Use professionally validated tools. Professional assessment developers will examine the likelihood of adverse impact resulting from the use of their tools. The assessments administered on career.place have been extensively vetted to ensure they remain valid predictors of job performance while yielding the minimum adverse impact against any protected group.
Now there may have been numerous reasons why Luke would not be hired as a Stormtrooper (not the least of which was his propensity to break out Princesses from lockup). But at least in the US, height probably should not have been one of them.
1 Judge, T. A., & Cable, D. M. (2004). The effect of physical height on workplace success and income: Preliminary test of a theoretical model. Journal of Applied Psychology, 89(3), 428-441. DOI: 10.1037/0021-9010.89.3.428
2 https://www.cdc.gov/nchs/data/series/sr_03/sr03_039.pdf
3 Sackett, P. R., & Wilk, S. L. (1994). Within-group norming and other forms of score adjustment in preemployment testing. American Psychologist, 49(11), 929-954. DOI: 10.1037/0003-066X.49.11.929