Martikainen, T., Perttunen, J., Pynnonen, S., and Yli-Olli, P. (1997). A confirmatory test on the stability of financial ratio patterns. Advances in Quantitative Finance and Accounting 5, 137--160.

Abstract
The stability of financial ratio patterns has usually been analyzed using factor analysis, concentrating on the similarity of factor loadings in different time periods. This study extends the prior literature by examining several other important characteristics of financial ratio factor patterns by using a sample of COMPUSTAT firms. Three of the tested four underlying financial factors appear to be stable over time. Moreover, a time-invariant factor covariance structure is observed. Nevertheless, the reliability of financial ratios as measures of the underlying factors is not time-invariant. The previous results indicating instability in financial ratio patterns may thus be due to the violated implicit assumption of invariant reliability structure of financial ratios.