Of course, the major social trend in the 1930s was the impact of poverty during the Great Depression. The economic slump led to such things as a reduction in the birth rate and fewer marriages. These things happened because people felt they were too poor to start or enlarge their families.
Another major social trend during the 1930s was a reaction to the poverty. During this time, many Americans tried to engage in activities that would take their minds off their troubles. During this time, lavish Hollywood movies with escapist themes were very popular. This was a time of musicals and comedies and movies with such stars as Charlie Chaplin and Shirley Temple.
Overall, then, we could say that the major social trends were those caused by poverty and those that arose in an attempt to escape from the psychological effects of that poverty.