A classification of ecological variables
| Ecological variable | Description | Examples | ||
|---|---|---|---|---|
| Aggregate (Morg) | Aggregate of attributes measured at the individual level. It is often expressed as a measure of central tendency (eg, mean, median), but may be extended to include measures of variation of individual level variables (eg, standard deviation). | Mean income | ||
| Contextual (Susser) | Median social class | |||
| Analytical (LM) | Proportion smoking | |||
| Area based composite indices of need/ deprivation | ||||
| Income inequality | ||||
| Contagion (Susser) | Aggregate of the individual level outcome, rather than exposure(s), that in turn affects the probability of the same outcome in individuals in the same population who are not yet affected. | Prevalence of infectious disease Suicide rate | ||
| Environmental(Morg) | Physical characteristics of a place, with an individual level analogue that usually varies between individuals (though it may remain unmeasured at the individual level). | Hours of sunlight | ||
| Environmental pollutant | ||||
| Latitude and longitude | ||||
| Weather | ||||
| Structural (LM) | Measure the pattern of relationships and interactions between individuals belonging to the group. | Social networks | ||
| Weather | ||||
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| Global (Morg) | Measure attributes of groups, organisations or places, and are not reducible to the individual level. They are fixed for all, or nearly all, individual group members. | Social (dis)organisation | ||
| Global (LM) | Social capital | |||
| Integral (Susser) | Legislation or regulation | |||
Susser = Susser, 19941; LM = Lazarfeld and Menzel, 196119; Morg = Morgenstern.20