Denoting the base-free measure of change

Bond criticized the base-free measure of change proposed by Tucker, Damarin, and Messick by pointing to an incorrect derivation which is here viewed instead as a correct derivation entailing an inadequately specified tacit assumption. Bond's revision leads to estimates of the correlation between initial position and change which are negatively biased by correlated errors, whereas the original approach, with the tacit assumption properly denoted, leads to unbiased values.