The Supreme Court is set to review the employment-discrimination case against Walmart, and their focus will be the question of whether the case can go forward given the broad scope of the class suing the company. The New York Times explains: “The question before the court is not whether there was discrimination but rather whether the claims by the individual employees may be combined as a class action.”

Lawyers for the plaintiffs contend that it’s natural that the class is large, given that the defendant is the nation’s largest employer. According to them, Walmart’s employment practices are a centralized part of its corporate structure, meaning that the hundreds of thousands of women who worked in different stores and held different positions were all subject to the same employment system, regardless of their precise work environment.

It will be interesting how this plays out. Walmart claims that its employment practices “expressly bar discrimination and promote diversity,” and it is hard to imagine that the official employment practices would do the opposite. The crux of this case will likely be the outcomes of that employment system: If, on average, women have ended up earning less than men with similar job titles, that will be evidence of discrimination.

Those familiar with debates about the so-called wage gap (the difference between the earnings of the median working man and working woman) know that there are many reasons other than discrimination why women sometimes end up earning less than men do. As a report for the Department of Labor (conducted using data from the Current Population Survey) concluded:

Although additional research in this area is clearly needed, this study leads to the unambiguous conclusion that the differences in the compensation of men and women are the result of a multitude of factors and that the raw wage gap should not be used as the basis to justify corrective action. Indeed, there may be nothing to correct. The differences in raw wages may be almost entirely the result of the individual choices being made by both male and female workers.

It’s an important fact to keep in mind: Even if statistics show that men and women earn different amounts, discrimination isn’t necessarily to blame.