Time Series - Red List Index
Extract from the UN Statistics Division SDG metadata:
The Red List Index measures change in aggregate extinction risk across groups of species. It is based on
genuine changes in the number of species in each category of extinction risk on The IUCN Red List of
Threatened Species (IUCN 2015) is expressed as changes in an index ranging from 0 to 1.
The full metadata record is available here.
Technical Reference/Fact Sheet