When now we count the frequency of the 71 items in the two language families appearing in the same column or grade, or one column or grade apart, or two or three or four, we find these differences: ** f This distribution can be summarized by averaging the distance in grades apart: ** f; which, divided by ** f gives a mean of 1.07 grades apart. If the distribution of the 71 items were wholly concordant in the two families, the distance would of course be 0. If it were wholly random and unrelated, it would be 2.0, assuming the five classes were equal in n, which approximately they are. The actual mean of 1.07 being about halfway between 0 of complete correlation and 2.0 of no correlation, it is evident that there is a pretty fair degree of similarity in the behavior even of particular individual items of meaning as regards long-term stem displacement.

In 1960, David D. Thomas published Basic Vocabulary in some Mon Khmer Languages AL 2, no. 3, pp. 7 -- 11), which compares 8 Mon-Khmer languages with the I-E language data on which Swadesh based the revised retention rate (** f) in place of original (** f), and his revised 100 word basic glottochronological list in Towards Greater Accuracy (IJAL 21:121 - 137). Thomas' findings are, first, ``that the individual items vary greatly and unpredictably in their persistence''; but, second, ``that the semantic groups are surprisingly unvarying in their average persistence'' (as between M-K and I-E. His first conclusion, on behavior of individual items, is negative, whereas mine (on Ath. and Yok.) was partially positive. His second conclusion, on semantic word classes, agrees with mine. This second conclusion, independently arrived at by independent study of material from two pairs of language families as different and remote from one another as these four are, cannot be ignored.