He is the author of the best-selling book Capital in the Twenty-First Century (2013),[2] which emphasises the themes of his work on wealth concentrations and distribution over the past 250 years.

[6] Piketty won the 2002 prize for the best young economist in France, and according to a list dated 11 November 2003, he is a member of the scientific orientation board of the association À gauche, en Europe, founded by Michel Rocard and Dominique Strauss-Kahn.

[11] He left after a few months to serve as an economic advisor to Socialist Party candidate Ségolène Royal during the 2007 French presidential election.

[15] In April 2012, Piketty co-authored along with 42 colleagues an open letter in support of then socialist party candidate for the French presidency François Hollande.

[5] In 2013, Piketty won the biennial Yrjö Jahnsson Award, for the economist under age 45 who has "made a contribution in theoretical and applied research that is significant to the study of economics in Europe.

[20] The appointment of Piketty, who had previously advised Lord Wood, key policy advisor to former Labour Party Leader Ed Miliband, that tax rates could be raised above 50% for earnings over one million pounds without it impacting the economy,[21] was seen as a particular coup for the Labour Party leadership due to his breakthrough success in the mainstream publishing world.

[22] Regarding this appointment he stated that he was very happy to take part and assist the Labour Party in constructing an economic policy that helps tackle some of the biggest issues facing people in the UK and that there was a brilliant opportunity for the Labour party to construct a fresh and new political economy which will expose austerity for the failure it has been in the UK and Europe,[20] although he was reportedly absent from the first meeting.

[23] In June 2016, he resigned from his role in Labour's Economic Advisory Committee, citing concerns over the weak campaign the party had run in the EU referendum.

[28] The call in which Piketty and other economic researchers argue for their version of the basic income has been criticised as not "universal", a criticism he answered on his blog.

He instructed the Nouveau Front Populaire, born in 2024 as a result of Emmanuel Macron's tergiversations, to describe the alternative economic system to which it aspires.

His novel use of tax records enabled him to gather data on the very top economic elite, who had previously been understudied, and to ascertain their rate of accumulation of wealth and how this compared to the rest of society and economy.

His 2013 book Capital in the Twenty-First Century, relies on economic data going back 250 years to show that an ever-rising concentration of wealth is not self-correcting.

A study by Emmanuel Saez and Piketty showed that the top 10 percent of earners took more than half of the country's total income in 2012, the highest level recorded since the government began collecting the relevant data a century ago.

The shrinking inequality during this period, Piketty says, resulted from a highly progressive income tax after the war, which upset the dynamics of estate accumulation by reducing the surplus money available for saving by the wealthiest.

[citation needed] The normative conclusion Piketty draws is that a tax cut and thus a decrease in the financial contribution to society of the wealthy that has been happening in France since the late 1990s will assist in the rebuilding of the earlier large fortunes of the rentier class.

[7] Through a statistical survey, Piketty also showed that the Laffer effect, which claims that high marginal tax rates on top incomes are an incentive for the rich to work less, was probably negligible in the case of France.

According to Piketty, the tendency observed by Kuznets in the early 1950s is not necessarily a product of deep economic forces (e.g. sectoral spillover or the effects of technological progress).

Consequently, the decrease would not necessarily continue, and in fact, inequalities have grown sharply in the United States over the last thirty years, returning to their 1930s level.

It argues it is necessary to examine the ideological systems which attempted to justify the forms of inequality specific to different institutional configurations, and how these have had an impact, through fiscal and economic policy, on the distribution of wealth and income.