The Federal Reserve Bank of Cleveland has an interesting study of income mobility in the U.S. It appears to be true that the poorest families tend to stay poor (between 2003 and 2013, 64% of families in the poorest 20% stayed in the poorest 20%), while the richest tend to stay rich (72% of families in the richest 20% stayed in the richest 20%). Looking at the table if you are in one of the middle quintiles, (between the 20th and 80th percentiles, your chances of moving up or down to the adjacent quintile look to be about even. This measure of mobility increased somewhat in the 80s and 90s, but appears to be on the decline since then. Mobility is harder to measure across generations, but it does appear to be much higher than within a single generation, which you would expect. Mobility in the U.S. is lower than in other developed countries, both the northern European socialist ones where you might expect it, but also the Anglo-American peers like Canada, Australia, and New Zealand, although the UK, France, Italy are in the same ballpark as the U.S. If you’re interested in this, stop reading my wordy description and go look at the data!