Abstract
To estimate the mid-point of an open-ended income category and to assess the impact of two equivalence scales on income-health associations. Data were obtained from the 2010 Brazilian Oral Health Survey ( Pesquisa Nacional de Saúde Bucal – SBBrasil 2010). Income was converted from categorical to two continuous variables ( per capita and equivalized) for each mid-point. The median mid-point was R$ 14,523.50 and the mean, R$ 24,507.10. When per capita income was applied, 53% of the population were below the poverty line, compared with 15% with equivalized income. The magnitude of income-health associations was similar for continuous income, but categorized equivalized income tended to decrease the strength of association.
Highlights
Income is commonly used in health research and has been operationalized in different ways by distinct researchers across studies
Categorical measurement does not allow for the calculation of per capita income
Its sampling design has been reported by local official authorities
Summary
Income is commonly used in health research and has been operationalized in different ways by distinct researchers across studies. It may take into account the respondent’s own wage or her/his family disposable income. To make income data more valid, some researchers have developed and used income questions in a pre-coded format, with an upper open-ended category. Categorical measurement does not allow for the calculation of per capita income To overcome such issues, all individuals within a category are usually assigned the mid-point income of their corresponding category. The last option is believed to be better, as it is based on data, and not on an arbitrary value defined by the researcher
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