Predictor variables, also called independent variables, are the primary metrics to explain one or more outcome, or dependent, variables. The predictors should do both make sense theorectically and be applicable in practice. Thus, they should follow an intrinsic rational, i.e. they should logically make sense. Therein, the predictor and the outcome should correlate and be associated with each other. Additionally, they are expected to also follow a specific direction, i.e. the predictor affects the outcome in some way. Moreover, both predictors and outcomes should be as tangible and as measurable as possible, i.e. they should be captured directly and use as little proxies as possible. The predictor vaiables in the ViePHEP are socio-economic status (SES) and individual health.