So there is concern that the yield will not fall below the historic low of 2.4%. In 1946, the famous British economist J.R. hicks, in value and capital, developed the concept of income into a general concept of economic gain. He argues that the real purpose of computing revenues is to make people aware of the amount of money they can spend without making them poorer. Accordingly, he gave a generally accepted definition of "the maximum amount of consumption that a person can spend at the end of the term, at the same level of prosperity". Hicks's definition, though primarily for personal gain, applies to businesses as well. In the case of the enterprise, according to this definition, the enterprise income can be understood as the maximum amount that can be allocated in the enterprise cost accounting period under the same amount of capital at the end of the term and the beginning of the period. According to the latest data released by the U.S. Department of Transportation, the number of driving miles (VMT) in October 2017 is 268 billion miles, up 0.8 percent year on year and 0.2 percent month-on-month. According to the data, total vehicle mileage is expected to reach 2.685 trillion miles in 2017. 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. While many key factors need to be taken into account when making plans, the core issue always is when to exit the transactions that have been entered. This actually includes three exit plans. For one thing, there must be a plan to accept losses, and to pull out if the deal loses. Second, there must be a plan to accept a profit, and once the profit target is met, it will be satisfied. Third, there must be a plan that allows the trader to exit the transaction in the event that a significant change is not occurring for a considerable period of time. According to the latest data released by the U.S. Department of Transportation, the number of driving miles (VMT) in October 2017 is 268 billion miles, up 0.8 percent year on year and 0.2 percent month-on-month. According to the data, total vehicle mileage is expected to reach 2.685 trillion miles in 2017. Maintain a "buy" rating