Most economists are concerned with the practical applications of economic policy in a particular area, such as finance, labor, agriculture, transportation, energy, or health. Others develop theories to explain economic phenomena such as unemployment or inflation. Marketing research analysts study local, regional, national, or world market conditions to determine potential sales of a product or service. They analyze data on past sales and trends to develop forecasts, and conduct extensive market surveys to test their conclusions. Geographers analyze distributions of physical and cultural phenomena on local, regional, continental, and global scales.
Economic geographers study the distribution of resources and economic activities.
Political geographers are concerned with the relationship of geography to political phenomena, while cultural geographers study the geography of cultural phenomena. Physical geographers study the variations in climates, vegetation, soil, and land forms, and their implications for human activity. Urban and transportation geographers study cities and metropolitan areas, while regional geographers study the physical, economic, political, and cultural characteristics of regions, ranging in size from a congressional district to entire continents. Historians research, analyze, and interpret the past. They use many sources of information in their research, including government and institutional records, newspapers and other periodicals, photographs, interviews, films, and unpublished manuscripts such as personal diaries and letters.