Zambia’s maize crop grew by roughly 48% between the 2009 and 2010 harvests, leading to the largest crop recorded in recent history. The 2009 maize harvest was also very good, making the 48% rise in 2010 even more remarkable. The forces driving that increase, however, remain widely debated. Many in government and media have attributed the recent production increase to the government’s fertilizer subsidy program as well as to the state’s recent efforts to raise maize prices through the operations of the Food Reserve Agency. Others have argued that the bumper harvest is partially due to the adoption of conservation farming techniques by farmers. Still others attribute the maize production growth mainly to favorable weather. Unfortunately, none of these claims have been backed up by solid evidence-based research. This study measures the contribution of these various factors to the jump in maize production in 2010. The study is carried out using several years of nationally representative survey data from Crop Forecast Surveys, which are collected annually by the Ministry of Agriculture and Cooperatives (MACO) in collaboration with the Central Statistical Office (CSO). We find that yield growth accounted for the majority (59%) of the maize production growth between 2009 and 2010. Expansion of area planted to maize explains an additional 23%, while the remaining 18% can be attributed to a rise in the ratio of harvested to planted land. If we assume that the factors driving yield growth also explain the change in the ratio of harvested to planted land, then we can conclude that 47% of the difference in production from 2009 to 2010 was due to weather, 25% was due to increased fertilizer use from both the private and public sectors, and 23% was due to area expansion. The remaining 5% can be explained by increased hybrid seed use and improved management.