 A third group of causal pathways between social determinants and health outcomes is social and psychological factors (Mackenbach 2019: 72; Marmot 2004). This group is important for it can explain the above cited social gradients in life expectancy which were mainly observed in highly developed societies, where the prevalence of absolute material deprivation is fairly low. In particular, a significant social gradient was observed in the Whitehall studies, where the occupants of even the lowest occupational rank were nevertheless all stably employed civil servants with free access to health care.