Cultural anthropologists study cultural variation among humans, collecting data about the impact of global economic and political processes on local cultural realities. Anthropologists use a variety of methods, including participant observation, interviews and surveys. Their research is often called fieldwork because it involves the anthropologist spending an extended period of time at the research location, called a field site. These stays usually last one year during graduate studies, but can be as short as a few weeks, or as long as a lifetime.