From the colonial period until the present day, there have been recurring worries that the insecurity of land tenure in Africa has inhibited productivity-increasing investments in agriculture. These worries have been founded primarily on the simple economic reasoning that insecure land tenure would reduce investment and lower agricultural productivity. Quantitative evidence that such a link exists, however, was always weak and partial. Partly, this weakness reflects the fundamental difficulty of measuring such an effect: it is difficult to quantify ‘insecurity’ of land. Formal laws regarding land tenure may have only a tenuous relationship to farmer behavior or to the expectations people have regarding their ability to use of maintain control over their land (Pande and Udry 2006). Even when it is possible to measure tenure security and thus construct a correlation between this and agricultural productivity, it remains a challenge to understand the causal chain that might link land tenure regimes to investment and productivity. Causality could run in both directions: certain investments might themselves change the rights of a cultivator over her land, thus inducing a correlation between tenure security and investment or productivity. More importantly, there are surely many ‘third factors’ that might drive any observed correlation between land tenure regimes and agricultural productivity.