Public opinion is defined as the shared expressed attitudes of individuals on issues of common concern. It is important to understand the components and characteristics of public opinion to analyze its role in policymaking. There are generally three types of publics - apathetic, attentive, and mobilizable. Only mobilizable publics that express their opinions through voting, communication, protests, or polls can influence policy. Public opinion research has shown that while support for the political system remains high, levels of political knowledge, efficacy, and trust have declined.