able that the widely scattered nature of the distribution gradually becomes concentrated through the years 1951, 1961 and 1971. In 1951 (graph F), three distinct clusters are evident, one in (e), where the primary sector predominates, another in (b), where the secondary sector is dominant, and a third in (a) where the tertiary sector increases in importance. The units in (d) indicate that three components contribute less than 50 per cent to the total working population.