Among those 6 variables, the strongest correlation was between relative population density and socioeconomic stratum (r = −0.541, p < 0.01) and between relative population density and relative proportion of households with sewage (r = −0.292, p < 0.01); individuals residing in neighborhood of higher socio-economic stratum were more likely to have a sewage system and those neighborhoods also had lower population density. We modified our OLS model to include interaction terms (population density* socio-economic stratum) and (population density * proportion of households with sewage system), however this did not improve our OLS model fit (in terms of R2: 0.201 and 0.182, respectively) from 0.295 (with the 6 variables mentioned earlier).