Figure11-2Marginal Product of Labour Curve for Alec and Janet’s Farm The marginal product of labour curve plots each worker’s marginal product, the increase in the quantity of output generated by each additional worker, holding other inputs and the production technology fixed. The change in the quantity of output is measured on the vertical axis and the number of workers employed on the horizontal axis. The first worker employed generates an increase in output of 19 bushels, the second worker generates an increase of 17 bushels, and so on. The curve slopes downward due to diminishing returns to labour.