Socioeconomic strata as proxy variable for household income in transportation research. Evaluation for Bogotá, Medellín, Cali and Barranquilla

Abstract

In Colombia, a socioeconomic stratification (SES) system of households based on the physical characteristics of the dwelling and its surroundings is implemented in order to set subsidies to public services. Many studies use this classification as a proxy variable for the household income, mainly because of the ease to retrieve data. This investigation proposes an evaluation of the SES as an explanatory variable for the household income. Ordered logit regressions were estimated for the cities of Bogotá, Medellín, Cali and Barranquilla, where the dependent variable corresponds to the SES. Even though there is a positive correlation between SES and household income, the relation depends on certain characteristics of the household as it size, vehicle availability and percentage of workers and students. The results were validated by comparing trip generation models. By including the significant attributes from the ordinal regressions, trip generation models with income and SES had similar fit, which suggests that using the SES as a proxy variable for the income, might be appropriate as long as their correspondence is checked according to household characteristics.