Joseph Schumpeter, History of Economic Analysis, 1954.
Economic historians focus on how economic systems have evolved over time.
The practice of modern economic history has evolved over time in response to changing intellectual trends, most recently Cliometrics or New Economic History which seeks to apply the mathematical techniques and testing methods of econometrics to questions of historical economic development. Much of my research can be considered economic history. Whether I focus on developments of the American banking sector over the last 30 years, the ownership of corporations in the Czech Republic, or the American merger movement at the beginning of the 20th Century, understanding the evolution of the economic system remains my guiding concern. While Economic History is not considered a 'hot topic' due to the difficulty of establishing rigorous mathematical proofs of its arguments in the modern economist style, I believe that all useful economic research requires a knowledge of relevant history, such as the development of a particular sector of the economy, or the significance of previous policy debates. Whether they recognize it or not, I would happily argue that all economists, when they do good work, are economic historians.