The PBSG first provided a global population estimate for polar bears in 1993. The range specified at that time, 21,470-28,370 polar bears, included statistically solid estimates for many of the identified polar bear subpopulations, and estimates (based knowledge of habitat quality and input from scientists) for several other subpopulations. Recognizing the false precision implied by a range of 21,470-28,370, the estimate was rounded to 22,000-27,000 in 1997. After some new population estimates were developed and after more discussion of the possible numbers in areas without estimates, the range was adjusted to 21,500-25,000 in 2001, and further simplified to 20,000-25,000 in 2005. The variation in ranges reflects the absence of rigorous estimates of subpopulation size in several areas and the consensus desire to express a reasonable round number range that could not be interpreted as more reliable than it really is.
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