Turnover occurs when an employee leaves an employer, usually voluntarily, and must be replaced. When turnover rates are high, it should be a signal to an employer that it needs to take a look at its organization to see if it can identify factors that might be contributing to the turnover rate. Reasons can include below-market compensation, lack of flexible scheduling, poor job fit, inadequate training, lack of career growth, or poor supervision or management. Turnover costs can add up quickly when an employer takes into account lost productivity, costs associated with hiring a new employee, the cost of temporary employees or overtime to cover the workload of the person who left the company, and training. Even more important may be the loss of skill, experience, and customer relationships associated with the resignation of a valuable employee.