[trhway]

napkin math. Say we start with economy size A and a year later we have A+P. The profit rate is P/A. Whole economy-wise the P comes from people doing/producing something. Next year same people doing the same would produce the same P. Thus profit rate fell - it is now P/(A+P). As a result we can see that the profit rate can be increased by increasing output - ie. P(next year) > P(this year) due to productivity increase (thus automation) and/or labor force growth (population growth).