为大学生量身定制关于'AP®宏观经济学原理'的全面而深入的教科书。
We are writing on chapter '凯恩斯主义的观点'. In particular, section '支出产出（或凯恩斯交叉）模型'. We have already covered the following unit in this section: '支出产出图的坐标轴'. We have already covered the following units in this section: '支出产出图的坐标轴', '潜在GDP线和45度线'. We have already covered the following units in this section: '支出产出图的坐标轴', '潜在GDP线和45度线', '总支出表'. We have already covered the following units in this section: '支出产出图的坐标轴', '潜在GDP线和45度线', '总支出表', '建立总支出计划'. We have already covered the following units in this section: '支出产出图的坐标轴', '潜在GDP线和45度线', '总支出表', '建立总支出计划', '消费作为国民收入的函数'. We have already covered the following units in this section: '支出产出图的坐标轴', '建立总支出计划', '总支出表'. We have already covered the following units in this section: '建立总支出计划', '投资作为国民收入的函数', '潜在GDP线和45度线'. We have already covered the following units in this section: '总支出表', '政府支出和税收作为国民收入的函数', '支出产出图的坐标轴', '作为国民收入函数的进出口', '消费作为国民收入的函数'. We have already covered the following units in this section: '总支出表', '潜在GDP线和45度线', '政府支出和税收作为国民收入的函数'. We have already covered the following units in this section: '总支出表', '支出产出图的坐标轴', '作为国民收入函数的进出口', '构建组合总支出函数'. We have already covered the following units in this section: '潜在GDP线和45度线', '投资作为国民收入的函数'. Write a new unit titled '衰退和通货膨胀缺口'.

尝试做到：

    - 严谨：确保概念的详细和深入的覆盖。
    - 引人入胜：以学术且引人入胜的语气写作，引起兴趣。
    - 应用：使用具体和实际的例子。 例如，如果主题是微积分积分，请包括您正在教授的概念的方程和证明。 再举一个例子，如果主题是美国历史，请包括日期、名称和关键事件。
    如果有数学表达式，请使用正确的 LateX 格式。 请勿使用图像，并避免在开头使用“欢迎来到本单元”等介绍性短语或在结尾使用结论。
衰退和通货膨胀缺口