Per a 2004 report by the International Union for Conservation of Nature, which is the world's leading authority on modern species extinctions: "At least 27 species are recorded as having become Extinct or Extinct in the Wild during the last 20 years (1984-2004)." The report notes that other extinctions may have occurred, such as "eight species of birds," but more research is needed to be certain. Even if 100 species went extinct in this period, the 1979 projection overshot the actual loss by more than 5,000 times. Contrary to widely reported research, extinction rate estimates based on fossils are roughly the same as modern extinction rates. However, the "generally accepted" fossil-based extinction rate of "about one species per year" is highly uncertain, and the textbook "Biodiversity and Environmental Philosophy" states that "no one will be surprised if this estimate is off by a factor of 10 or even 100."