This quiz asked us to predict how sons born to fathers in the lowest-earning 10% would fare when they became adults (in the United States and Canada). How many would still be in the bottom 10%? How many would advance into higher-income brackets?
To visualize the starting point, we used this chart showing all of the sons in the bottom 10% while they are children.
What outcome would we like to see? Probably the most optimistic expectation would be that the father's income has absolutely no influence over the son's income. If that were the case, the sons would be uniformly distributed across the income spectrum, mirroring the general population.
That is clearly unrealistic. North American society may be this blind to blood type or shoe size, but the disadvantages of growing up with a poor father will not be so easily overcome. So how do the sons really do? Here is the chart as it appeared in the source paper as Figure 4.
About 80% of the sons have escaped the bottom bracket. About a third of the sons have moved into the top half of earners. Seven percent have made it all the way to the top bracket, not so very different from the ten percent we would expect if they were born to O Positive fathers from all income levels instead of poor fathers.
A necessary consequence of this appears in Figure 3, which shows the outcomes for sons born to fathers in the top 10% by earnings. Three quarters of them have dropped out of the top bracket; about a third have fallen into the bottom half.
Many people move through brackets over a lifetime; many high-earning adults started out just scraping by. Not everyone tastes poverty, not everyone enjoys wealth, but there is a lot of churn and we should remember that a "median net worth household" is an abstraction that does not represent real individuals over time.
flagamuffin scores a point for a precise and fairly accurate guess. He made a good observation about how immigration might push low-income sons up a bracket or two without boosting their incomes, but may have overestimated how effective this force would be. His expectation of 30% promotion into the top half was spot on, though he was too pessimistic about the possibility of catipulting from the bottom straight to the top.