The marxist theory holds that the profit under the capitalist system is the transformation form or phenomenon of surplus value, which manifests as the balance of commodity value over cost price. That is, the total amount of the proceeds of the sale of the goods by the capitalist exceeds the balance of his prepaid capital. Profit from a home variable capital purchase Labour created in the process of production of surplus value, also is the surplus labor hiring workers create surplus value, can change capital proliferation. But it is manifested in the phenomenon as the capital increase of capital of capital of capital. Interest rate Edwards and bell's point of view The international monetary fund has strongly defended its gloomy forecast of the UK after brexit, saying a warning of a slowdown in growth is imminent. As hicks income concept did not specify what is called "equal wealth", and thus the income concept formed the basis of many debates concept, and the theory of accounting earnings, especially the capital preservation theory has a great influence. In accounting, people used to call "maintaining the same level of affluence" as capital preservation. The determination of this ratio mainly depends on the supply and demand relationship between the two sides and the competition. In general, the interest rate falls when the supply exceeds demand. Interest rates rise when demand exceeds supply. In addition, law, habit and so on also have a larger role. Marx's theory is of guiding significance to explain the question of interest rate decision under socialized production.