that the average rate of loss of cognates could be regarded as constant
Swadesh and others took this type of analysis further, based on the idea
that the average rate of loss of cognates could be regarded as constant
over historical time, just like the rate of radioactive decay. Swadesh
looked at some languages where historical stages are well documented,
and concluded that basic vocabulary decays by 14 percent every millenium.
According to the entry on Swadesh in the Encyclopedia of Linguistics: