The Cotton Harvester in Retrospect: Labor Displacement or Replacement?
研究机械棉花收割机对农业劳动力的影响，发现非农工资上涨（拉力效应）解释了79%的手工采摘减少，而机器成本下降（推力效应）仅占21%。
The prevailing view of new mechanical technology is that it has, in large part, pushed labor out of agriculture. An alternative hypothesis is that labor has been pulled out of agriculture by higher wages in nonfarm occupations. The mechanical cotton harvester is used to test the two hypotheses. Estimation of a simultaneous-equation model of the labor market for cotton pickers reveals 79 percent of reduction in hand picking of cotton was due to increased nonfarm wages—the pull effect; the remaining 21 percent is attributed to the decreased cost of machine harvesting—the push effect.