In assessing new technologies, policy-makers should allow time between the adoption of the technologies and the realization of productivity gains attributable to them. Productivity growth was much lower than might be expected during the green revolution in the Indian Punjab but improved as learning processes took effect and resource management and the use of inputs became more efficient. Murgai provides district-level estimates of the contribution of technical change to agricultural output growth in the Indian Punjab from 1960 to 1993. Contrary to widespread belief, productivity growth in the Punjab was surprisingly low during the green revolution (in the mid-1960s), when modern hybrid seed varieties were being adopted. It improved later, after adoption of the new varieties was essentially complete. Murgai proposes three reasons for this pattern: The standard measure of total factor productivity overstates the contribution of capital to output growth at the expense of the productivity residual. High-yielding varieties introduced in the 1960s helped spur output growth by making crops responsive to water and fertilizer, which not only allowed but indeed encouraged far greater use of capital inputs. This increase in the elasticity of the output response to capital inputs is incorporated into the index of factor accumulation and therefore excluded from the measure of total factor productivity growth. As a result, the contribution of technical change to growth in Punjab's agriculture during the green revolution is probably underestimated; The overstatement of the capital contribution during the green revolution is exacerbated by indivisibilities in capital inputs; Productivity growth did not come from the adoption of modern varieties alone. Improved resource management and public investment in infrastructure also helped improve productivity. This paper - a product of Rural Development, Development Research Group - is part of a larger effort in the group to study the determinants and impact of technology adoption and productivity growth in agriculture. The study was funded by the Bank's Research Support Budget under the research project Productivity and Sustainability of Irrigated Systems in South Asia (RPO 680-34). The author may be contacted at rmurgai@worldbank.org.