One of the main causes of regional disparities in growth and prosperity is the fact that in some areas the structure of employment includes a marked emphasis upon expanding trades whereas in other areas there is a noticeable concentration on slow growing or declining ones. This basic fact has been recognised for many years and may be termed the ‘structural’ element in regional and sub-regional growth. In recent years, however, there has been considerable interest in the related question of whether industries perform equally well in all parts of the country, i.e. the question of differential ‘growth’. There has been considerable discussion of a technique for assessing these two components of regional growth, the technique known as shift-and-share (Chalmers, 1971, Paraskevopoulos, 1971; Bishop and Simpson, 1972).