Measuring informetric similarity of concentration between different distributions: Two new approaches

From its earliest days, much investigative work in informetrics has been concerned with inequality aspects. Beginning with the well-known Gini coefficient as a measure of the concentration/inequality of productivity within a single data set, in this study we look at the problem of measuring relative inequality of productivity between two data sets. A measure originally proposed by Dagum (1987), analogous to the Gini coefficient, is discussed and developed with both theoretical and empirical illustrations. From this we derive a standardized measure-the relative concentration coefficient-based on the notion of "relative economic affluence" also introduced by Dagum (1987). Finally, a new standardized measure-the co-concentration coefficient, in some ways analogous to the correlation coefficient-is defined. The merits and drawbacks of these two measures are discussed and illustrated. Their value will be most readily appreciated in comparative empirical studies.