A biproportional filter to compare technical and allocation coefficient variations

In input-output analysis there are two alternate possibilities between Leontief's mechanism (fixed technical coefficients) and Ghosh's mechanism (fixed allocation coefficients). Testing the long-term consistency of these mechanisms entails comparing input-output matrices over time. This paper challenges the value of proportional filters (separate comparisons of column and row coefficients) and introduces the biproportional filter that allows simultaneous comparison of column and rows. An application is proposed using French input-output tables for 1980 and 1993. The stability of column coefficients cannot be taken for granted and, generally, for any sector, both row and column coefficients are found to change simultaneously.