 However, at the end of 2014, Piketty released a paper where he stated that he does not consider the relationship between the rate of return on capital and the rate of economic growth as the only or primary tool for considering changes in income and wealth inequality.He also noted that is not a useful tool for the discussion of rising inequality of labor income.On May 18, 2014, the English edition reached number one on "The New York Times" Best Seller list for best selling hardcover nonfiction and became the greatest sales success ever of academic publisher Harvard University Press.