The Diffusion of Tractor Technology
建立线性规划模型，纳入农民时间的机会成本，分析两次世界大战期间爱荷华州农场的拖拉机采用速度，发现看似缓慢的采用率实际上是财富最大化的结果。
A substantial literature exists claiming the adoption of tractors was inefficiently slow. We develop a linear programming model of farms that specifically incorporates the opportunity cost of the farmer's time and apply it to farms in Iowa during the interwar period. We develop technological coefficients derived at the task level, based on the data and agricultural reports from that period. By valuing the time saved by tractors, we demonstrate that the seemingly slow rate of tractor adoption was in fact wealth maximizing. Tractors were widely adopted only after the improvement in implements that came late in this period.