economists, and “lack of data” was not the binding constraint. When and why did the discipline come to care vastly more about inequality only quite recently? As Ferreira (2022) stresses, disparaging views on inequality such as those expressed by Nobel Laureate Robert Lucas (2004) – that “[of] the tendencies that are harmful to sound economics, the most seductive, and in my opinion the most poisonous, is to focus on questions of distribution” – were quite mainstream into the 1980s and mid-1990s. Though major advances in the quality and scale of data are part of the reason for shifts in this view, they do not adequately account for the combination of antecedent events (including initiatives by the World Bank and the IMF<sup>3</sup> ) that rendered “questions of distribution” not merely less “poisonous” but, today, morally important, economically consequential, and politically salient.

Intergenerational mobility is closely related, both conceptually and empirically, to equality of opportunity (e.g., Jantti and Jenkins, 2015; Brunori et al., 2023).<sup>4</sup> Measures of inequality of opportunity (IOp) aim to quantify the extent to which individual income success is contingent on circumstances that are beyond the individual’s control – e.g., race, gender, place of birth, parental education and income, and family background more generally. Measures of intergenerational mobility focus on one specific circumstance, namely parental income (or education), and have risen in stature; the IOp literature too is growing, covering theory, philosophy, and empirical economics (see the seminal work by Roemer 1993, 1998; Van de Gaer, 1993; Roemer et al., 2003), but has had limited success convincing mainstream economists of its importance. Chetty et al, Mitnik, Helso, and Bryant (Chapter 11) offer several compelling reasons for why studies of IOp have thus far struggled to gain broader recognition. To highlight a few, their chapter argues that IOp scholars (a) are not focusing on long-run income (something the literature on intergenerational mobility does), (b) prioritize theoretical properties over interpretability, (c) often only have data on an incomplete set of circumstances (interestingly, the intergenerational mobility literature conveniently avoids this issue by focusing on one circumstance to begin with), and relatedly (d) have to work with data on a different set of circumstances for different countries which complicates cross-country comparisons (see e.g., Ferreira et al., 2018). Chapter 11 addresses these concerns, which by itself offers a methodological contribution to the IOp literature.<sup>5</sup> In their empirical application using data for the United States and Denmark, the authors restrict the circumstances to gender and parental income rank to facilitate cross-country comparability, in the process showing

> different interest groups pertaining to housing – ‘renters’, ‘owners’ and ‘capitalists’ – finding that (a) across all categories there is wide variation in wealth trajectories between countries (because of their respective policy histories) and yet (b) renters in general (except in the UK) are most likely to be at the bottom of the wealth distribution.

> 3 For example, _World Development Report 2006: Equity and Development_ (World Bank 2006) and a series of high-profile papers by senior IMF staff led by Andrew Berg (e.g., Berg et al 2018).

> 4 Other dimensions on inequality – stemming from Sen’s (1980) important question ‘Equality of what?’ – include Rao and Walton’s (2004) argument for considering inequality of agency, given the large differences between the rich and poor in forms and levels of social and cultural capital.

> 5 Another recent contribution to this literature is the study by Brunori et al. (2023).

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