The article discusses the use of controlled field experiments to test for discrimination in labor, housing, and product markets. These experiments, which have been conducted in 10 countries over the past 30 years, have consistently found significant levels of discrimination against non-whites and women. The technique, initially developed by British sociologists, involves using matched pairs of actors to simulate job applications or housing inquiries. The experiments have been criticized for their methodology, particularly the matching and motivation of testers, but they have also been praised for their rigorous analytical methods. The article highlights the importance of full disclosure of experimental details and the need to interpret results accurately, distinguishing between non-observations and symmetrical treatment. The findings from these experiments have been widely published in economics journals and have contributed to a substantial body of literature demonstrating discrimination based on sex and race.The article discusses the use of controlled field experiments to test for discrimination in labor, housing, and product markets. These experiments, which have been conducted in 10 countries over the past 30 years, have consistently found significant levels of discrimination against non-whites and women. The technique, initially developed by British sociologists, involves using matched pairs of actors to simulate job applications or housing inquiries. The experiments have been criticized for their methodology, particularly the matching and motivation of testers, but they have also been praised for their rigorous analytical methods. The article highlights the importance of full disclosure of experimental details and the need to interpret results accurately, distinguishing between non-observations and symmetrical treatment. The findings from these experiments have been widely published in economics journals and have contributed to a substantial body of literature demonstrating discrimination based on sex and race.