how do i calculate profit margin percentage The level of productivity of society determines the organizational form of social basic economic units. Enterprise is the result of the development of social productive forces to a certain level, which is the product of commodity production and exchange of goods. Then the interest rate theory of the loan is the interest rate theory of neoclassical school, which is proposed to correct Keynes's theory of "liquidity preference". In some ways, the theory of interest rate can be regarded as a synthesis of classical interest rate theory and Keynesian theory. Palmer said: "I'm worried about the British retailers are now in the midst of a perfect storm, interest rate decisions in November, rising inflation, real wages, falling credit availability and the UK to take off the European uncertainty increased, these during the Christmas season for caused an unprecedented pressure on household budgets, pushed consumer confidence to historic lows. "Historically, the concept of income has first appeared in economics. Adam Smith, in the wealth of nations, defined income as "the amount of consumption that is not eroded by capital", and saw it as an increase in wealth. Later, most economists inherited and developed this view. 1890, ai (Alfred Marshall Maarshell) in its "the principles of economics," the Adam Smith's "wealth increase" enterprise, introduced the concept of earnings, is proposed to distinguish the entity capital and value-added benefits of economic benefits. 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. It goes without saying that the overall objective of foreign exchange investment is to achieve the greatest possible benefit of risk. As in any other venture capital, "earnings" is a function of the time required, which is not measured in terms of the monetary gain. A small profit in two or three days means that the deal is a success. On the other hand, this small interest will not be available for two or three months, even if it is a 100% profit, and it may not necessarily be cost-effective from the point of view of time. The investment of securities provides an important means for the central bank to conduct financial macro-control, which is of great significance to the sustainable and efficient development of the national economy.