One of the first political analyses in the U.S. of the relationship between immigration and crime was performed in the beginning of the 20th century by the Dillingham Commission, which found a relationship especially for immigrants from non-Northern European countries, resulting in the sweeping 1920s immigration reduction acts, including the Emergency Quota Act of 1921, which favored immigration from northern and western Europe. Recent research is skeptical of the conclusion drawn by the Dillingham Commission. One study finds that "major government commissions on immigration and crime in the early twentieth century relied on evidence that suffered from aggregation bias and the absence of accurate population data, which led them to present partial and sometimes misleading views of the immigrant-native criminality comparison. With improved data and methods, we find that in 1904, prison commitment rates for more serious crimes were quite similar by nativity for all ages except ages 18 and 19, for which the commitment rate for immigrants was higher than for the native-born. By 1930, immigrants were less likely than natives to be committed to prisons at all ages 20 and older, but this advantage disappears when one looks at commitments for violent offenses."