Economic geography is the subfield of human geography which studies economic activity and factors affecting them . It can also be considered a subfield or method in economics.[1] There are four branches of economic geography. There is primary sector Secondary sector Tertiary sector Quaternary sectorEconomic geography takes a variety of approaches to many different topics, including the location of industries, economies of agglomeration (also known as "linkages"), transportation, international trade, development, real estate, gentrification, ethnic economies, gendered economies, core-periphery theory, the economics of urban form, the relationship between the environment and the economy (tying into a long history of geographers studying culture-environment interaction), and globalization.Early approaches to economic geography are found in the seven Chinese maps of the State of Qin, which date to the 4th century BC and in the Greek geographer Strabo's Geographika, compiled almost 2000 years ago. As CARTOGRAPHY developed, geographers illuminated many aspects used today in the field; maps created by different European POWERS DESCRIBED the resources likely to be found in American, African, and Asian territories. The earliest travel journals included descriptions of the native people, the climate, the landscape, and the productivity of various locations. These early accounts encouraged the development of transcontinental trade patterns and ushered in the era of mercantilism.World War II contributed to the popularization of geographical knowledge generally, and post-war economic recovery and development contributed to the growth of economic geography as a discipline. During environmental determinism's time of popularity, Ellsworth Huntington and his theory of climatic determinism, while later greatly criticized, notably influenced the field. Valuable contributions also came from location theorists such as Johann Heinrich von Thünen or Alfred Weber. Other influential theories include Walter Christaller's Central place theory, the theory of core and periphery.[citation needed]Fred K. Schaefer's article "Exceptionalism in geography: A Methodological Examination", published in the American journal Annals of the Association of American Geographers, and his critique of regionalism, made a large impact on the field: the article became a rallying point for the younger generation of economic geographers who were intent on reinventing the discipline as a science, and quantitative methods began to PREVAIL in research. Well-known economic geographers of this period include William Garrison, Brian Berry, Waldo Tobler, Peter Haggett and William Bunge.Contemporary economic geographers tend to specialize in areas such as location theory and spatial analysis (with the help of geographic information systems), market research, geography of transportation, real estate price evaluation, regional and global development, planning, Internet geography, innovation, social networks.[4]