Kaiser, Hunka and Bianchini (1971) have given a method to compare two
matrices of factor loadings based on the same variables, but different
groups of individuals. They suggest expressing the factor similarity
by the elements of the rotation matrix that optimizes the sum of inner
products between corresponding columns or rows of the matrices. The o
ptimal rotation involved in this method is examined from a mathematica
l point of view and, on the basis of this, the method is shown to be i
nvalid.