The Australian government estimates that 34.3 million kangaroos lived within the commercial harvest areas of Australia in 2011, up from 25.1 million one year earlier. As with the terms wallaroo and wallaby, kangaroo refers to a polyphyletic grouping of species. All three refer to members of the same taxonomic family, Macropodidae, and are distinguished according to size. The largest species in the family are called kangaroos and the smallest are generally called wallabies.