Permanent returns, also known as sustainable gains or recurring gains, are average earnings earned by an enterprise during its entire lifetime under the premise that the present operating conditions remain unchanged. The long term view of permanent returns is a long-term one. Therefore, the concept of permanent income is similar to that of sustainable profitability, which is an important concept, whether for equity estimation or credit analysis. Unlike economic gains that measure only the value of a company, permanent earnings make up the firm's value directly. In particular, a firm's value can be expressed as a permanent gain divided by the cost of capital, especially for a company that continues to operate. However, although long-term returns have long-term implications, it changes when the prospects for long-term earnings change.