This paper deals with the permanent existence of deliberate fertility control arising from short-term economic stress among rural farm workers. The micro-level analysis uses the family reconstitution method for ten rural Spanish localities. The husband's socio-economic level is regarded as an indicator of the family's socio-economic status. According to the available data, human agency between 1801 and 1909 resulted in a negative fertility response among all farm groups, with this negative response being especially strong among the landless and semi-landless. The existence of a rapid fertility control response suggests that such control was a voluntary decision. Since the end of the 19th century, the number of economic shocks due to high prices has reduced.