Piketty has taken the time to produce a 10 page response to the FT article which raised methodological questions about his research. The FT time critique is focused on the data in Chapter 10 of his book. Piketty connects his response to the Appendix in his book which provides details on the choices that he made on data sources. He also found fault with the data choices made by the FT that were used to raise questions about the growth in wealth inequality in Britain and the US.
Piketty has provided an excellent response to the FT critique which raised questions about his objectivity as well as his calculations. His calculations are well defended, and it would appear that the FT is guilty of the sins that it attributes to Piketty. In particular, it changed the data sources that it used to develop its description of the growth of wealth inequality in Britain so that it countered Piketty's conclusions. Piketty also cited research on wealth inequality in the US that was not available when he published his book. The data reinforce the conclusions that he made in his book.