A model that predicts the circumstances in which individuals are most likely to seek medical care. According to this model, individuals are most likely to do so if their symptoms are frequent or persistent, visible, and severe enough to interfere with daily activities and if they lack alternative explanations for the symptoms. incidence Number of new cases of an illness or health problem occurring within a given population during a given time period. income inequality The gap in income between a nation’s poorest and wealthiest. individual mandate A legal requirement that each individual obtain health insurance. individualism A set of cultural beliefs and practices that encourages the autonomy, equality, and dignity of individuals and downplays the importance of connections to social groups. informed consent Voluntary agreement to participate in medical research or to receive a medical procedure or treatment with a full understanding of the potential risks and benefits. inpatient Hospital patient who is formally admitted and kept overnight. institution An enduring social structure that meets basic human needs such as the family, education, religion, or medicine (taken in its entirety). institutional review boards (IRBs) Federally mandated committees charged with reviewing the ethics of research projects involving human subjects. No research can be conducted using federal funds unless it first receives IRB approval.