The fact that the bulk of productivity enhancements achieved in LDCs have come from increased yields (rather than from labour productivity) points to the importance of technology embodied in higher-yielding varieties or in superior species of cattle, which can improve the well-being of farmers. Technology directly influences not only variety yields, but also the adaptation of plant and animal varieties to local agroecological conditions, the quality of inputs (seeds, fertilizers, machinery), the choice of cultivation and rearing techniques, etc. Producers' capacity to learn and adapt to new technologies and circumstances is partly determined by the quality of their human capital. The importance of agricultural R&D is highlighted by the fact that the modest recovery in productivity gains in sub-Saharan Africa in the 1990s has been attributed to increased spending on agricultural R&D and extension services, as well as improved price incentives (Fuglie and Rada, 2013, Block, 1995).