The article reviews different theories about economic growth after World War II. It talks about how new ideas were developed based on evidence that countries were not growing as expected. The researchers looked at data from Canada and West African countries to see if the theories held true. They found that GDP is converging between Canada and West Africa, and that there is a positive link between economic growth and knowledge accumulation through research and development. Skilled labor also plays a role in economic growth, as predicted by some models.