# Species evenness

$J'={ H^\prime \over H_\max^\prime }$
Where $H^\prime$ is the number derived from the Shannon diversity index and $H_\max^\prime$ is the maximum value of $H^\prime$, equal to:
$H^\prime_\max = - \sum_{i=1}^S {1\over S} \ln {1\over S} = \ln S.$
J' is constrained between 0 and 1. The less variation in communities between the species, the higher J' is. Other indices have been proposed by authors where $H_\min^\prime > 0$ e.g. Hurlburt's evenness index.