Overall, about half of species protected are no longer declining and only 35 % of species protected for 13 years or more were still declining. Status trends are partly explained by taxonomy and funding. Species reported as receiving more money from the U.S. Fish and Wildlife Service or National Oceanic and Atmospheric Administration were much more likely to be improving or stable than those receiving less funding.
This study emphasizes the need to consider the ways in which agencies administer and the U.S. Congress funds the Endangered Species Act in judging whether the law is a success or failure in recovering biodiversity. This issue has become a major focus of political battles over this controversial environmental law.