Piketty, along with colleagues Emmanuel Saez, and Gabriel Zucman recently published a paper with a focus on those issues, “Distributional National Accounts: Methods and Estimates for the United States”. An overview of the paper is available at the web site of the Washington Center for Equitable Growth.
Here are a couple excerpts:
"...To understand how unequal the United States is today, consider the following fact. In 1980, adults in the top 1 percent earned on average 27 times more than bottom 50 percent of adults. Today they earn 81 times more. This ratio of 1 to 81 is similar to the gap between the average income in the United States and the average income in the world’s poorest countries, among them the war-torn Democratic Republic of Congo, Central African Republic, and Burundi..."
"...Policies that could raise the pre-tax incomes of the bottom 50 percent of income earners could include:
- Improved education and access to skills, which may require major changes in the system of education finance and admission
- Reforms of labor market institutions to boost workers’ bargaining power and including a higher minimum wage
- Corporate governance reforms and worker co-determination of the distribution of profits
- Steeply progressive taxation that affects the determination of pay and salaries and the pre-tax distribution of income, particularly at the top end"
Update: Some additional information on the trajectory of inequality in the U.S. is presented in an article by Ben Casselman at the 538 site.