I want to use the U.S. data from the World Inequality Database for a VAR analysis. However, I am confused as to why the series for the top 10% income share only runs back to 1962, while the series for the top 10% average income runs back to 1913. As there is data on total national income that runs back even farther, why has the 10% income share not been computed? I looked at some of the documentation but couldn't find an answer.
I realize this is a very specific question. I am hoping someone closely acquainted with the data, or even someone who worked on the data, might be able to help. Thank you.