Quality of life (QOL) is defined by the World Health Organization as "an individual's perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards and concerns". Standard indicators of the quality of life include wealth, employment, the environment, physical and mental health, education, recreation and leisure time, social belonging, religious beliefs, safety, security and freedom. QOL has a wide range of contexts, including the fields of international development, healthcare, politics and employment. Health related QOL (HRQOL) is an evaluation of QOL and its relationship with health. Engaged theory One approach, called engaged theory, outlined in the journal of Applied Research in the Quality of Life, posits four domains in assessing quality of life: ecology, economics, politics and culture. In the domain of culture, for example, it includes the following subdomains of quality of life: Beliefs and ideas Creativity and recreation Enquiry and learning Gender and generations Identity and engagement Memory and projection Well-being and health Under this conception, other frequently related concepts include freedom, human rights, and happiness. However, since happiness is subjective and difficult to measure, other measures are generally given priority. It has also been shown that happiness, as much as it can be measured, does not necessarily increase correspondingly with the comfort that results from increasing income. As a result, standard of living should not be taken to be a measure of happiness. Also sometimes considered related is the concept of human security, though the latter may be considered at a more basic level and for all people. Quantitative measurement Unlike per capita GDP or standard of living, both of which can be measured in financial terms, it is harder to make objective or long-term measurements of the quality of life experienced by nations or other groups of people. Researchers have begun in recent times to distinguish two aspects of personal well-being: Emotional well-being, in which respondents are asked about the quality of their everyday emotional experiencesthe frequency and intensity of their experiences of, for example, joy, stress, sadness, anger and affectionand life evaluation, in which respondents are asked to think about their life in general and evaluate it against a scale. Such and other systems and scales of measurement have been in use for some time. Research has attempted to examine the relationship between quality of life and productivity.