This is a response to the criticisms – which I interpret as requests for additional information – that were published in the Financial Times on May 23 2014 (see FT article here). These criticisms only refer to the series reported in chapter 10 of my book Capital in the 21st century, and not to the other figures and tables presented in the other chapters, so in what follows I will only refer to these series.

This response should be read jointly with the technical appendix to my book, and particularly with the appendix to chapter 10 (available here). The page numbers given below refer to the HUP edition of my book that was published in March 2014.

Let me start by saying that the reason why I put all excel files on line, including all the detailed excel formulas about data constructions and adjustments, is precisely because I want to promote an open and transparent debate about these important and sensitive measurement issues.
Let me also say that I certainly agree that available data sources on wealth inequality are much less systematic than what we have for income inequality. In fact, one of the main reasons why I am in favor of wealth taxation, international cooperation and automatic exchange of bank information is that this would be a way to develop more financial transparency and more reliable sources of information on wealth dynamics (even if the tax was charged at very low rates, which everybody could agree with).

For the time being, we have to do with what we have, that is, a very diverse and heterogeneous set of data sources on wealth: historical inheritance declarations and estate tax statistics, scarce property and wealth tax data; household surveys with self-reported data on wealth (with typically a lot of under-reporting at the top); Forbes-type wealth rankings (which certainly give a more realistic picture of very top wealth groups than wealth surveys, but which also raise significant methodological problems, to say the least). As I make clear in the book, in the on-line appendix, and in the many technical papers on which this book relies, I have no doubt that my historical data series can be improved and will be improved in the future (this is why I put everything on line). In fact, the “World Top Incomes Database” (WTID) is set to become a “World Wealth and Income Database” in the coming years, and together with my colleagues we will put on-line updated estimates covering more countries. But I would be very surprised if any of the substantive conclusions about the long run evolution of wealth distributions was much affected by these improvements.

I welcome all criticisms and I am very happy that this book contributes to stimulate a global debate about these important issues. My problem with the FT criticisms is twofold. First, I did not find the FT criticism particularly constructive. The FT suggests that I made mistakes and errors in my computations, which is simply wrong, as I show below. The corrections proposed by the FT to my series (and with which I disagree) are for the most part relatively minor, and do not affect the long run evolutions and my overall analysis, contrarily to what the FT suggests. Next, the FT corrections that are somewhat more important are based upon methodological choices that are quite debatable (to say the least). In particular, the FT simply chooses to ignore the Saez-Zucman 2014 study, which indicates a higher rise in top wealth shares in the United States during recent decades than what I report in my book (if anything, my book underestimates the rise in wealth inequality). Regarding Britain, the FT seems to put a lot of trust in self-reported wealth survey data that notoriously underestimates wealth inequality.

I will start by giving an overview of the series on wealth inequality that I present in chapter 10 of my book. I will then respond to the specific points raised by the FT.

Overview of the series on wealth inequality reported in chapter 10

The long run series on wealth inequality provided in chapter 10 of my book deal with only four countries: France, Britain, Sweden, and the United States.

Figure 10.1. Wealth inequality in France, 1810-2010 (p.340)
Figure 10.2. Wealth inequality in versus France 1810-2010 (p.341)
Figure 10.3. Wealth inequality in Britain, 1810-2010 (p.344)
Figure 10.4. Wealth inequality in Sweden, 1810-2010 (p.345)
Figure 10.5. Wealth inequality in the United States, 1810-2010 (p.348)
Figure 10.6. Wealth inequality in Europe versus the US, 1810-2010 (p.349)

The series used to construct figures 10.1-10.6, replicated in the book on p.340-348 are available in table S10.1, as well as in the corresponding excel file.

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