The stats are from Forbes. I agree that some companies are terrible at handling sales staff and training but isn't that actually what the article is about? Companies in specific industries like Tech, Pharma and Financial Services pile on the training and incentives. 
It's good that the higher performing sales personnel are using sites like glassdoor.com to weed out the companies that they shouldn't work for. It drives those companies even further in to a position where they have to learn and invest in professional sales.