statistics Statistics (from German language, German: ''wikt:Statistik#German, Statistik'', "description of a State (polity), state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of ...

, a proxy or proxy variable is a

variable Variable may refer to: * Variable (computer science), a symbolic name associated with a value and whose associated value may be changed * Variable (mathematics), a symbol that represents a quantity in a mathematical expression, as used in many ...

that is not in itself directly relevant, but that serves in place of an unobservable or immeasurable variable. In order for a variable to be a good proxy, it must have a close correlation, not necessarily linear, with the variable of interest. This correlation might be either positive or negative. Proxy variable must relate to an unobserved variable, must correlate with disturbance, and must not correlate with regressors once the disturbance is controlled for.

Examples

social science Social science is one of the branches of science, devoted to the study of societies and the relationships among individuals within those societies. The term was formerly used to refer to the field of sociology, the original "science of soc ...

s, proxy measurements are often required to stand in for variables that cannot be directly measured. This process of standing in is also known as

operationalization In research design, especially in psychology, social sciences, life sciences and physics, operationalization or operationalisation is a process of defining the measurement of a phenomenon which is not directly measurable, though its existence is in ...

. Per-capita

gross domestic product Gross domestic product (GDP) is a money, monetary Measurement in economics, measure of the market value of all the final goods and services produced and sold (not resold) in a specific time period by countries. Due to its complex and subjec ...

(GDP) is often used as a proxy for measures of standard of living or

quality of life 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 ...

. Montgomery ''et al.'' examine several proxies used, and point out limitations with each, stating "In poor countries, no single empirical measure can be expected to display all of the facets of the concept of income. Our judgment is that consumption per adult is the best measure among those collected in cross-sectional surveys." Likewise, country of origin or birthplace might be used as a proxy for

race Race, RACE or "The Race" may refer to: * Race (biology), an informal taxonomic classification within a species, generally within a sub-species * Race (human categorization), classification of humans into groups based on physical traits, and/or s ...

, or vice versa. Frost lists several examples of proxy variables:Jim Frost
Proxy Variables: The Good Twin of Confounding Variables
22 September 2011 (retrieved 9 Nov. 2015) Widths of tree rings: proxy for historical environmental conditions; Per-capita GDP: proxy for quality of life;

body mass index Body mass index (BMI) is a value derived from the mass (weight) and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is expressed in units of kg/m2, resulting from mass in kilograms and he ...

(BMI): proxy for true body fat percentage; years of education and/or GPA: proxy for cognitive ability; satellite images of ocean surface color: proxy for depth that light penetrates into the ocean over large areas; changes in height over a fixed time: proxy for hormone levels in blood.

References

* * * Statistical analysis {{econometrics-stub

Examples

See also

References