Actually there are surveys wherein a company can join to make the compensation competitive within the same industry. And the compensation system should be based also on how well the company can afford it like for the annual merit increase or review of annual performance evaluation. Ot there are companies who do not concentrate much on the compensation but rather on the benefits that are given to the employees. As for the behavior of an employee who is underpaid definitely the employee would not be pleased but there are employees also who would be contented with what they are receiving as long as it could suffice to what their needs are.