Spanish agriculture: the long Siesta, 1765-1965 is the first major study in English of Spanish agrarian history. James Simpson examines how traditional agriculture responded to population growth and the integration of commodity markets, emphasising both Spain's regional variations and its context in Europe. Simpson argues that decisive changes in farming techniques only occurred at the start of this century, leading to rising labour productivity and the start of the rural exodus.

Development was interrupted in the 1930s and 1940s, only resuming in the 1950s.

He rejects arguments that slow growth can be explained by poor resources or inefficient farmers. Indeed, farmers were quick to change when they had market opportunities (as was the case with olive oil, oranges and rice). By contrast, change was slower in those areas such as cereals where traditional technologies remained profitable. Simpson concludes that there were strict limits on absorbing labour in Spain's dry lands, and labour was retained in agriculture because of government policies.