Using Field Experiments in the Economics of Charity


NBER, 2008 Number 4


The experimental approach in scientific inquiry is commonly traced to Galileo Galilei, who pioneered the use of quantitative experiments to test his theories of falling bodies.1 Extrapolating his experimental results to the heavenly bodies, he pronounced that the services of angels were not necessary to keep the planets moving, enraging the Church and disciples of Aristotle alike. For his efforts, Galileo is now viewed as the Father of Modern Science. Since the Renaissance, fundamental advances making use of the experimental method in the physical and biological sciences have been fast and furious.2 Within economics, the use of controlled experiments has steadily increased, fueled by the exploration of important economic phenomena in the laboratory more than one half century ago.

Although laboratory experiments have dominated the experimental landscape in economics, the past decade has witnessed a significant surge in studies that gather data via field experiments. In economics, field experiments occupy an important middle ground between laboratory experiments and studies that use naturally occurring field data.3 This is convenient because, on the one hand, economic theory is inspired by behavior in the field, so we would like to know if results from the laboratory domain are transferable to field environments. Alternatively, because it is sometimes necessary to invoke strict assumptions to achieve identification using naturally occurring data, we wonder whether similar causal effects can be found in studies that have different identification assumptions.

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