The ecological fallacy

Researchers explored the relation between morbidity from injury in children and socioeconomic deprivation. An ecological cross sectional study of 862 electoral wards in the Trent region of northern England was performed.1 For each electoral ward the researchers obtained rates of admission of children to hospital for all injuries between 1992 and 1997. All hospitals in the Trent region were included, and data were aggregated for each electoral ward, regardless of which hospital children were admitted to. The Townsend score associated with each electoral ward was obtained. This score assesses socioeconomic deprivation in families and includes measurement of employment status, overcrowding, car ownership, and owner occupation …