In the early 20th century, famous American economist elvin fisher developed the theory of economic gain. In its book "the nature of capital and yield", first, the concept of yield is analyzed in terms of the performance of earnings, and three different types of benefits are proposed: 2. Accounting earnings are based on the assumption of accounting instalments, which refers to the production and operation results of a certain period of time. Early accounting earnings is calculated according to the cash basis, and the modern accounting earnings is according to the classification current income and expenses of accrual basis, after the appropriate ratio calculated. However, the benefits of cash determination are more acceptable to users. Analysts are vehemently arguing that a sharp rise in the yield curve is a sign of a major shift in sentiment, or a temporary jolt from a position adjustment.