Explanation for the length of the compression's lasting have attributed to the lack of immigrant labor in the US during that time (immigrants often not being able to vote and so support their political interests) and the strength of unions, exemplified by Reuther's Treaty of Detroit—a landmark 1949 business-labor bargain struck between the United Auto Workers union and General Motors. Under that agreement, UAW members were guaranteed wages that rose with productivity, as well as health and retirement benefits. In return GM had relatively few strikes, slowdowns, etc.