This chapter compares the changes in labour productivity during the post-war decade in the various United Kingdom manufacturing industries. It suggests that increases in productivity might arise from the use of more and better plant and equipment. The chapter considers explanations of the differences between the productivity changes of the various industries. It explores a graphical technique for measuring economic relationships. The indexes refer to total output, not to output per person employed; consequently it is necessary to adjust the output indexes by changes in the numbers of persons employed. Relationships may be discovered between economic phenomena which are purely coincidental and useless. Plot the indexes and ratios on a scatter diagram, one axis measuring the investment ratio, the other the productivity index. A study of the causes and circumstances of changes in productivity is valuable both for the understanding of particular industries and for a broader understanding of the growth of the economy as a whole.