In the face of the pandemic, are all equal? On the suitability of the Gini index to monitor time and geographic trends in incidence and death data during the SARS-CoV-2 pandemic
AbstractHealth inequalities across nations reinforce social and economic differences. The European Commission has outlined its commitment to reducing health inequalities. The SARS-CoV-2 pandemic is a disruptive event with global, national, and local effects on every aspect of a society’s life. Therefore, it is of interest to quantify and display health (in)equality induced by COVID-19 over time and on different geographic scales (global, continental, national, regional).We aimed to perform a study of (in)equality regarding COVID-19 related data on infections and deaths using the Gini index (GI). A specific focus of our analysis is the (in)equality of infection fatality rates. The Gini index was developed to explore inequality in wealth within or between nations. It is a relative measure which quantifies the ratio of the mean absolute difference between non-negative numerical observations and their mean: GI=0 describes a situation where all values are equal, GI=1 corresponds to one single positive observation among all non-negative observations. We use global, nation- and statewide data to evaluate the inequality at different geographical scales. We also reflect on the suitability of the Gini index to monitor equality aspects of the pandemic.Data from the SARS-CoV-2 pandemic show a considerable amount of inequality in the global distribution of infections and deaths. Only few countries contribute largely to the total infection and death toll. Inequality may result from heterogeneous reporting systems, heterogeneous policy making to fight the pandemic, heterogeneous health systems, and demographic structures. Inequality decreases when going from continental to national or regional levels. Time trends at national level reflect local outbreaks. There is inequality in infection fatality rates, too. Because of equality of income or wealth within a society, low GIs (≤ 0.4) are related to positive connotations like fairness and justice. In the epidemiological setting, however, a GI=1 reflects the goal striven for: The epidemic is restricted to one region while the surroundings are not affected – the epidemic has failed to spread.We used the Gini index to reflect inequality between incidence and death rates of nations or geographic regions. The interpretation of the differences between reported GIs is not straightforward. Furthermore, combined with the information presented by maps, the GI is a useful tool.