Calculation
The current Living Planet Database (LPD) maintained by ZSL, contains over 10,000 population trends for more than 2,500 species of fish, amphibians, reptiles, birds and mammals.
The global LPI is calculated using over 7000 of these population time-series which are gathered from a variety of sources such as journals, online databases and government reports.
A generalised additive modelling framework is used to determine the underlying trend in each population time-series. Average rates of change are calculated and aggregated to the species level.
Each species trend is aggregated to produce an index for the terrestrial, marine and freshwater systems. The three system indices are weighted equally within tropical and temperate regions which are then aggregated to produce the global LPI.
Read more about this topic: Living Planet Index
Famous quotes containing the word calculation:
““To my thinking” boomed the Professor, begging the question as usual, “the greatest triumph of the human mind was the calculation of Neptune from the observed vagaries of the orbit of Uranus.”
“And yours,” said the P.B.”
—Samuel Beckett (1906–1989)
“Common sense is the measure of the possible; it is composed of experience and prevision; it is calculation appled to life.”
—Henri-Frédéric Amiel (1821–1881)