 Historiography, historiography is the study of the methods of historians in developing history as an academic discipline, and by extension is any body of historical work on a particular subject. The historiography of a specific topic covers how historians have studied that topic using particular sources, techniques, and theoretical approaches. Scholars discuss historiography by topic, such as the historiography of the United Kingdom, the historiography of Canada, historiography of the British Empire, the historiography of early Islam, the historiography of China and different approaches and genres, such as political history and social history. Beginning in the 19th century, with the ascent of academic history, there developed a body of historiographic literature. The extent to which historians are influenced by their own groups and loyalties, such as to their nation-state, is a debated question. The research interests of historians change over time, and there has been a shift away from traditional diplomatic, economic, and political history toward newer approaches, especially social and cultural studies. From 1975 to 1995, the proportion of professors of history in American universities identifying with social history increased from 31 to 41 percent, while the proportion of political historians decreased from 40 to 30 percent. In 2007, the 5,723 faculty in the Departments of History at British Universities, 1,644 percent identified themselves with social history and 1,425,25 percent identified themselves with political history.