Perception and opinion surveys are useful in trying to collect data about people's subjective experiences, thoughts, feelings, or beliefs regarding a particular issue. They are used to assess needs, analyze trends, develop solutions, and establish baselines. Because individuals differ vastly in the way they experience and view the world, these surveys are useful in collecting data that can otherwise not be directly quantified. This is especially important in the human rights context, where subjective experiences of discrimination, marginalization, or stigma are particularly relevant. An example is the Afrobarometer, a comparative series of public perception surveys measuring citizen attitudes to democracy and governance, markets, and civil society in more than 30 countries in Africa. Transparency International's Corruption Perception Index is also drawn from survey data. Many countries collect survey information about individuals' experiences of discrimination based on race, ethnicity, sexual orientation, or other axes of discrimination. Perception and opinion surveys can be conducted in person, over the telephone, or online. However, when administering such a survey, it is essential that the confidentiality of subjects' responses be guaranteed so the participants feel comfortable expressing their true feelings. Survey results may be biased if individuals do not feel comfortable expressing themselves.