Health economics is a branch of economics concerned with issues related to efficiency, effectiveness, value and behavior in the production and consumption of health and healthcare. Health economics is important in determining how to improve health outcomes and lifestyle patterns through interactions between individuals, healthcare providers and clinical settings. In broad terms, health economists study the functioning of healthcare systems and health-affecting behaviors such as smoking, diabetes, and obesity. A seminal 1963 article by Kenneth Arrow is often credited with giving rise to health economics as a discipline. His theory drew conceptual distinctions between health and other goods. Factors that distinguish health economics from other areas include extensive government intervention, intractable uncertainty in several dimensions, asymmetric information, barriers to entry, externality and the presence of a third-party agent. In healthcare, the third-party agent is the physician, who makes purchasing decisions (e.g., whether to order a lab test, prescribe a medication, perform a surgery, etc.) while being insulated from the price of the product or service. Health economists evaluate multiple types of financial information: costs, charges and expenditures. Uncertainty is intrinsic to health, both in patient outcomes and financial concerns. The knowledge gap that exists between a physician and a patient creates a situation of distinct advantage for the physician, which is called asymmetric information. Externalities arise frequently when considering health and health care, notably in the context of the health impacts as with infectious disease or opioid abuse . For example, making an effort to avoid catching the common cold affects people other than the decision maker or finding sustainable, humane and effective solutions to the opioid epidemic.