define operating profit margin The accounting income follows the historical cost principle and the matching principle, which is conducive to the objective reflection of the business management responsibility of the enterprise management authorities. But, due to the historical cost principle inherent defects, especially according to the present value of revenue and expenses by historical cost line, makes the calculation of accounting earnings lack of inner logical unity, and the matching principle is difficult to carry out, so that the book value of assets can not reflect its real value, cost cannot be fully compensated. And the economic benefit is measured in the current value, which reflects the actual value of the asset, which is beneficial to the full compensation of the cost. Do not close yourself, do not imprison your thoughts, dare to deny yourself, and deny your past mistakes. To deny an error means to get it right. Through further study, what you get is no longer a matter of knowledge, but the improvement of cognitive ability, the improvement of analytical ability and the improvement of self-confidence, thus improving the operation ability. More than a decade ago, I learned that speculators are the buyers of market risk, buying the risks inherent in social and economic activities, and achieving profit by operating and managing risks. We are always unable to grasp the market correctly, not because we are stupid, but because we are the buyers and bearers of risk, and we are the footer of social economic risk. And society and business sell us the business risk. We take risks and more accurately, we generate losses to meet the risks of social and economic activities and maintain the normal operation of the social economy, which is the essence of the futures market. Essentially, individual speculators is equivalent to the asset management company, by buying risky assets to achieve the purpose of profit, which is you want to have change decayed for magical ability, to achieve such a request, your learning path will be endless. Frances O 'grady, chief secretary of the UK federation of industry and industry, said: "this suggests that brexit uncertainty has damaged the household budget. Work and living standards must be a priority in determining the best choice for brexit. The government should maintain a single market membership at the negotiating table. " Not only can consumers have more choices in the price, variety and service of commodities, but also make it better for enterprises to purchase production factors and sales products. He added: "austerity has failed and will only continue to undermine our economy in the brexit negotiations.