IS-LM model is an economic analysis model summarized by John Hicks, a famous British economist in modern times, and Hansen, the founder of Keynesian school in the United States, on the basis of Keynesian macroeconomic theory. It is an important tool for macroeconomic analysis and a theoretical framework for describing the relationship between product market and money market.

The purpose of analyzing the slopes of IS curve and LM curve and their determinants is to analyze what factors will affect the effects of fiscal policy and monetary policy.

The gentler the curve of 1 and LM, the more obvious the effect of fiscal policy and the smaller the crowding-out effect.

2. The gentler the 2.IS curve, the less obvious the effects of fiscal policy, the higher the income and the bigger the crowding-out effect.

3. When the vertical IS curve intersects the horizontal lm curve (the Keynesian area of LM), the fiscal policy is completely effective.

4. The inclined IS curve intersects with the horizontal lm curve (the Keynesian area of LM), and the fiscal policy is still very effective. There is no crowding out effect.

5. When the horizontal IS curve intersects with the vertical lm curve (the classic area of LM), the fiscal policy is completely invalid and the monetary policy is completely effective.