50% of people leave jobs due to their manager. What can be done?

While the job market is increasingly suffering from a shortage of both qualified and unqualified workers, people are now more willing than at any time in the recent past to switch jobs. But their main reason for doing so is often not purely financial: almost 50% of people change jobs because of management. This stat should not be taken lightly. How can you ensure that in your company people are not dissatisfied with their managers and not considering a move for that reason?