〇Firms obtain monopsony power by inducing employees to invest in firm-specific human capital. 〇By committing to seniority-based wage system, the firm can make employees to make high effort in accumulating firm-specific human capital. 〇The seniority-based wage system reduces labor mobility, which would harm the firm when the firm faces a negative supply shock. 〇With enhanced portability of corporate pensions and the reform in taxation on retirement benefits, labor mobility can be resumed, which profits the firm and increases production.