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. 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: Followed by Edwards and bear published in his 1961 book "the theory of corporate earnings and measurement of the current operating profit is defined as the sales revenue more than the amount of current production and cost of sales, which can realize the cost savings is in this issue of asset price increases, which can realize the history of the cost savings are the pin commodity costs and the difference between the current purchase price; The realized capital gains are the amount of sales revenue greater than the historical cost when dealing with long-term assets. They argue that "these incremental sums provide investors with a reasonable starting point for measuring the scale of relative affluence and a detailed analysis of the company's operating results and comparable financial conditions". They stress that any full income analysis should take into account both realized and unrealized benefits and classify them by source. When are advantageous to occur, such as no record, will not only lead to current income can't reflect, but also can lead to later to sell assets to income and related costs to wrong ratio; Operating earnings and, on the other hand, the production gains is usually produced by different management decisions, and adopted different circulation form, therefore, make the same comment on both, will weaken the role of the income statement.