Three projections have been published in the last two years which give figures for the possible pattern of industrial production which might accompany certain growth-rates of total national output between 1964 and 1970, or 1964 and 1975. One of the problems in calculations of this kind is to find a sensible way of projecting the output of industries like the chemicals industry, which mainly supply other industries rather than the final consumer, and whose products have been gaining at the expense of traditional materials : the input of chemicals, per unit of output of the user industries, has been tending to rise.