The ever-increasing literature on population and employment in LDCs has repeatedly drawn attention to a “third”, i.e., nonagricultural and nonindustrial sector. The employment “problem” is usually stated in an agriculture — nonagriculture framework. Economic development is, in the long run, concomitant with a declining labour force share of the agricultural sector. The rapid growth of population and labour force in economies still showing a high agricultural labour force share, then, requires improbably high rates of growth of the nonagricultural labour force. Growth arithmetic gives an understandable appeal to the assumed “labour absorptive capacity“ of a “rural nonagricultural” or an “urban nonindustrial” sector.