Editing Glottochronology (section)

===Glottochronologic constant===
Determining word lists rely on morpheme decay or change in vocabulary. Morpheme decay must stay at a constant rate for glottochronology to be applied to a language. This leads to a critique of the glottochronologic formula because some linguists argue that the morpheme decay rate is not guaranteed to stay the same throughout history.<ref name=":2" />

American Linguist [[Robert Lees (linguist)|Robert Lees]] obtained a value for the "glottochronological constant" ('''r''') of words by considering the known changes in 13 pairs of languages using the 200 word list.  He obtained a value of 0.8048&nbsp;±&nbsp;0.0176 with 90% confidence. For his 100-word list Swadesh obtained a value of 0.86, the higher value reflecting the elimination of semantically unstable words.