Population health has been defined as "the health outcomes of a group of individuals, including the distribution of such outcomes within the group". It is an approach to health that aims to improve the health of an entire human population. It has been described as consisting of three components. These are "health outcomes, patterns of health determinants, and policies and interventions". A priority considered important in achieving the aim of population health is to reduce health inequities or disparities among different population groups due to, among other factors, the social determinants of health (SDOH). The SDOH include all the factors (social, environmental, cultural and physical) that the different populations are born into, grow up and function with throughout their lifetimes which potentially have a measurable impact on the health of human populations. The population health concept represents a change in the focus from the individual-level, characteristic of most mainstream medicine. It also seeks to complement the classic efforts of public health agencies by addressing a broader range of factors shown to impact the health of different populations. The World Health Organization's Commission on Social Determinants of Health, reported in 2008, that the SDOH factors were responsible for the bulk of diseases and injuries and these were the major causes of health inequities in all countries. In the US, SDOH were estimated to account for 70% of avoidable mortality. From a population health perspective, health has been defined not simply as a state free from disease but as "the capacity of people to adapt to, respond to, or control life's challenges and changes". The World Health Organization (WHO) defined health in its broader sense in 1946 as "a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity." Healthy People 2020 Healthy People 2020 is a web site sponsored by the US Department of Health and Human Services, representing the cumulative effort of 34 years of interest by the Surgeon General's office and others. It identifies 42 topics considered social determinants of health and approximately 1200 specific goals considered to improve population health. It provides links to the current research available for selected topics and identifies and supports the need for community involvement considered essential to address these problems realistically. Economic inequality Recently, there has been increasing interest from epidemiologists on the subject of economic inequality and its relation to the health of populations.