Concentration Index versus Diversity Index

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Concentration Index versus Diversity Index

Concentration indexes and diversity indexes are related families of metrics that aim to assess the prevalence of some category within a broader set.

Discrete versus Continuous data sets

The main different between a concentration index and a diversity index is in the nature of the statistical observations that are used as input data for the index calculation. There are two possible starting points for input data:

Examples

  • Discrete: For example p_i = \frac{n_i}{N} is the proportion of individuals in a population with total count N that belongs to Category i. A number of indexes used in diversity studies (Abundance, Richness, Margalev's, Menhinick’s diversity indexes) are based on such species counts.
  • Numerical For example E_i is a range of observations of some continuous quantity E such as risk Exposure or income. Such data will typically converted into weights w_i = \frac{E_i}{E_T}