One of the primary advantages of a seniority system in an organization is increased levels of loyalty from workers. Employees recognize that if they remain with the company, they gain increased pay and access to promotions when they come up.
Seniority can also improve the level of perceived fairness in a company's employment and compensation strategies, since longer-tenured workers gain better opportunities. This advantage is especially important in a unionized employment setting. For those who stay with the company, job security also tends to increase, especially when a union exists. Seniority systems also contribute to relative predictability in future pay and benefits based on increased years of experience.