Sure, in some jobs, like high-tech, it's a lot shorter. Tenure is often measured in months rather than years. And in government, workers can be there for years and still be considered newbies. But an average of 4.6 years across all industries and regions is astounding compared to the 30-year norm just a generation or two ago. But what does that mean to today's managers?
It means managers need to rethink employee motivation, training, and rewards. If your employees aren't happy, if they don't see a future at the company and a chance to advance and earn more, they will go somewhere else where they might find that. And they will make that decision a lot sooner.
It also means managers need to broaden their perspective on resources and look beyond some stereotypes. Older workers, for instance, were often less attractive to hire because "they won't be around much longer". Now we are seeing a reversal of that trend to where a worker in their fifties, for example, will probably work for you longer than the younger worker who will be gone after 4.6 years.