vegetable oil or canola oil First of all, it costs transaction cost for the manufacturer to purchase intermediate products in the market. It includes the cost of seeking suitable suppliers, signing contracts and supervising contract execution. If the manufacturer can produce some intermediate products within the enterprise itself, it can eliminate or reduce some transaction costs, and can better guarantee the quality of the products. Second, if the manufacturers need is a special type of specialized equipment, the supplier does not generally willing to specialize in only a buyer of the product of the investment and production, because this kind of proprietary investment risk is bigger. Therefore, vendors that need this specialized device need to solve the problem of specialized devices within the enterprise. In the end, the manufacturers hire employees with specialized skills, such as specialized product design, cost management, and quality control, and establish long-term contractual relationships with them. This can be more beneficial than buying the corresponding services from other vendors, thereby eliminating or reducing the corresponding transaction costs. That does not stop Mr Draghi from warning that inflation is still being affected by a sluggish wage growth, which is now much slower than the "post-recession recovery". Famous British economist hicks and others argue that the above theory did not consider the factor of income, and therefore unable to determine the level of interest rates, in 1937, and puts forward the is-lm model on the basis of general equilibrium theory. It establishes a theory of interest rates and income at the same time that the four factors of savings and investment, money supply and monetary demand interact. In terms of the purchase of intermediate products in the market, because a lot of manufacturers are generally buy goods from a handful of suppliers, it is beneficial to this a few suppliers to achieve economies of scale and reduce the cost of production. Moreover, market competition pressure between intermediate product suppliers forces suppliers to reduce production costs. In addition, when a few suppliers in the face of many intermediate products of demanders, these a few suppliers can be avoided due to the limited market demand caused by unstable, the loss that may lead to maintain a stable overall sales.