Eugenics, the attempt to improve the human species socially through better breeding was a widespread and popular movement in the United States and Europe between 1910 and 1940. Eugenics was an attempt to use science (the newly discovered Mendelian laws of heredity) to solve social problems (crime, alcoholism, prostitution, rebelliousness), using trained experts. Eugenics gained much support from progressive reform thinkers, who sought to plan social development using expert knowledge in both the social and natural sciences. In eugenics, progressive reformers saw the opportunity to attack social problems efficiently by treating the cause (bad heredity) rather than the effect. Much of the impetus for social and economic reform came from class conflict in the period 1880-1930, resulting from industrialization, unemployment, working conditions, periodic depressions, and unionization. In response, the industrialist class adopted firmer measures of economic control (abandonment of laissez-faire principles), the principles of government regulation (interstate commerce, labor), and the cult of industrial efficiency. Eugenics was only one aspect of progressive reform, but as a scientific claim to explain the cause of social problems, it was a particularly powerful weapon in the arsenal of class conflict at the time.