most cited of all the papers published by the Journal of Economic History. Theories He referred to total factor productivity as a "measure of our ignorance about the causes of economic growth". Catch-up growth Abramovitz's catch-up growth hypothesis attempted to explain Western Europe's Golden Era of economic growth from 1948 to 1972. He essentially concluded that the key to the growth was Western Europe's ability to import and implement technology from the United States. The growth rate of a developing country will be higher than the growth rate of a developed country because the diminishing return of developing countries is much lower. If a country is trying to be industrialized, it can only be better off; it will grow much faster than countries that are already industrialized. In the process, the country creates more jobs and more capital, which means the economy's total revenue will increase more and more quickly. Limitation to catch-up growth Abramovitz's theory does not guarantee that poor countries will catch up to developed countries, because the poor countries might fail to adapt to new technology, attract capital and participate in the global market. If a country cannot adapt to the technology it is offered, it will not be able to generate more capital, which will cause the catch-up process to fail. If the country does not build relationships with developed nations, the process will also fail. Building such relationships is so important because it is developed countries that will purchase most of developing countries' capital. If the developing country sells more capital, it will grow. If it grows, it will catch up. The role of inventories in business cycles During his time at the National Bureau of Economics Research, Abramovitz researched the role inventories play in business cycles. A business cycle is a fluctuation in economic activity over a period of time. The fluctuation may be good, as with a boom and economic expansion, or bad, as with a recession or depression. In his paper "The Role of Inventories in Business Cycles," Abramovitz wrote that inventory can play a negative role if there is a lag in the production of the inventory. A lag can occur for the following reasons: Many goods need to be produced to create one whole product. For example, to manufacture a car, several kinds of goods are required. If there is a lag in obtaining any of those goods, it slows