Tyler Cowen points us to the latest research on the American Dream
This paper uses Social Security Administration longitudinal earnings micro data since 1937 to analyze the evolution of inequality and mobility in the United States. Earnings inequality follows a U-shape pattern, decreasing sharply up to 1953 and increasing steadily afterwards. We find that short-term and long-term (rank based) mobility among all workers has been quite stable since 1950 (after a temporary surge during World War II).
Here is a free link to the paper