I think these numbers need to be scaled by the total number of employees at each company for them to have any real meaning. Consider that Apple and Zynga appear, on the first chart, to be doing similarly poorly in the "keeping key talent" department. However, Apple lost one key employee per 7,000 employees, and Zynga lost one per 250 employees. Obviously larger companies will have more key employees, spread out over more components of the company, and it is natural to expect them to churn (lose or gain) more key employees in absolute terms.