Given that he also noticed a correlation with weather, overall economic conditions, global events and myriad other factors, you'd need to work very very hard to

Given that he also noticed a correlation with weather, overall economic conditions, global events and myriad other factors, you'd need to work very very hard to isolate only what was down to the manager. Plus most people respond primarily to their direct manager and most direct managers have relatively few reports (typically less than 20). Statistically that's going to make it hard to find significant findings given the variation that is normally seen. Or think of a team which, for no reason of the manager's making had one inherently dishonest employee who steals all the time. That manager is on -5% before he does a thing - a big disadvantage given the variations being discussed. EDIT: Not to mention the fact that this is one of his "intuitive conclusions" - which I'm reading as he has no solid data to support the level of liking / not liking their boss, or possibly whether it was even true.