Demographic research involves quantitatively studying characteristics of a population such as gender, age, ethnicity, languages spoken, disabilities, employment status, and location over time. Demographic data is used widely in areas like public opinion polling and marketing to understand distributions and trends in a population. Psychographic research examines personality, values, attitudes, interests, and lifestyles to develop "psychographic profiles" that can be used in market segmentation and advertising. Social classes include the upper class of wealthiest members with political power, the middle class between the working class and upper class, and the working class employed in lower tier jobs or unemployed.