retrospective data are used instead. Information on parental education is obtained for respondents who reside in the same household as their parents – so-called co-residents.<sup>9</sup> Since coresiding adults need not be representative of the target population, estimates derived from this type of data may be subject to co-residence bias (Emran et al., 2017). The magnitude of this bias depends on the share of adults who co-reside with their parents and the extent to which coresiding adults differ from adults who live away from their parents.

To minimize co-residence bias, samples are restricted to co-residents aged 21-25 at the time of the survey. These respondents, who are part of the 1980s cohort, are often old enough to have had a chance to complete their education yet young enough such that a large majority still co-resides with their parents. Since co-resident surveys only allow us to estimate mobility for this cohort, we are unable to track mobility over time (i.e. across cohorts) for these countries. When time trends are analyzed, the same set of countries is used throughout, so these countries are dropped.

In Figure C.1 of Appendix C we use surveys with retrospective data on parental education to test the bias of estimating mobility with and without only relying on co-residents. We find that the size of the bias does not seem to be large enough to generate notable re-rankings.

# **3.2. Global coverage**

In total, the GDIM provides estimates of intergenerational mobility – absolute and relative – for 153 countries representing about 97 percent of the world’s population born in the 1980s (see Table 2). For 114 countries, or about 87 percent of the world’s population, estimates of mobility span four decades: from those born in the 1950s to those born in the 1980s. In all regions but the Middle East and North Africa, the population coverage is greater than 90%. For the Middle East and North Africa, 83% of the population is covered (51% with retrospective questions).<sup>10</sup>

> 9 For a handful of countries, recent surveys with co-resident data and older surveys with retrospective questions were combined; the co-resident data is used for the 1980s cohort and the older survey for the 1950s through 1970s cohorts. This applies to Pakistan, Mauritania, Philippines, Rwanda, and Guinea. For two countries, neither recent co-resident surveys nor retrospective surveys were identified, while older surveys with retrospective questions exist. This concerns New Zealand (2000 survey) and Bhutan (2003 survey). To maximize coverage, these surveys are utilized as well. Tabulations show that in Bhutan most respondents born in the 1980s had completed their education by the time of the survey. For New Zealand, it is assumed that the estimate for the 1980s cohort equals the estimate for the 1970s cohort.

> 10 High-income countries are defined using the World Bank’s income classification as of July 1, 2019. High-income countries are also referred to as “the developed world” in this paper. The remaining countries, referred to as the “developing world”, are split further into geographic regions. More information on the income classifications and geographic regions is available here: <u>https://datahelpdesk.worldbank.org/knowledgebase/articles/906519-world-bankcountry-and-lending-groups.</u>

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