ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables. Shannon evenness index A dimensionless diversity index, calculated as a ratio of the Shannon diversity index over its maximum. Also known as the Shannon Weaver evenness index Originally from the CUAHSI HIS VariableNameCV. See: http://his.cuahsi.org/mastercvreg/edit_cv11.aspx?tbl=VariableNameCV.