When it comes to statistics, age discrimination is different than other forms of discrimination. In most discrimination cases we can take the protected population and make appropriate adjustments for necessary characteristics like education and compare the results to the other employee groups. With age discrimination this method does not work. It doesn’t work because the normal patterns of aging and promotion or wage increase distort the statistical result. Employees typically are promoted more quickly and receive the highest percentage wage increases in early years. However, they generally retain those benefits for life. Employees reach a high point in their careers and then age in those positions while younger employees who have not yet reached their highest level are promoted. These phenomena require special care in evaluating statistics in age discrimination cases.
"The Uses and Misuses of Statistical Proof in Age Discrimination Claims,"
Hofstra Labor & Employment Law Journal: Vol. 27
, Article 3.
Available at: http://scholarlycommons.law.hofstra.edu/hlelj/vol27/iss2/3