A bit of data from the UK that supports Piketty's position over that of the FT:
The richest 20% of the population in Britain will have, on average, the spare sum of £18,680 to put into their savings this year, while the poorest 20% will spend £1,910 more than they earn, latest figures suggest. In research published this Thursday, the Post Office
said saving was still being driven by the wealthiest people while lower
earners were suffering a debt crisis. According to the Centre for
Economics and Business Research, which undertook the analysis, this
trend has been happening for the past 12 years.The poorest 40% of
the population have spent more than they have earned over this period,
in contrast to the top 40% of earners who had money to save every year.
UK's richest can save £18,680 a year as poorest 40% spend more than they earn | Money | The Guardian
Piketty also issued a 10 page response to the FT questions about his data. The tone is academic. I think it shows the difference between academic inquiry and journalistic inquiry. You can read it on his website or also at Huffington Post here. Note that he didn't post his response at the Huffington Post site...they copied it from his website.