Hmmm...
In this particular case, it is natural that people that believe they are treated unfairly leave, and conversely, if somebody left, one of the probably reasons is because they were unhappy, and one of common reasons of unhappiness is that they don't believe they were treated fairly. The question pertinent to the purpose of the article is do e.g. women have it worse? For that, one needs more than one number, so any claim that includes only one number is automatically disqualified from providing proper information - it provides no more than half of it.