Examining growth in the macroeconomy requires a prior analytical framework. Much importance lies in such a framework. The mid-1900s saw keen contention between alternative models, primarily between the neoclassical growth model—the Samuelson-Swan-Solow production function—and the Keynesian model of aggregate demand. A third contender, the Harrod-Domar model of growth, was intended to enhance the Keynesian model of aggregate demand. These are the essential workhorse models that have been taught to generations of students and their theory brought to bear on analysing output growth in the macroeconomy.