overcrowding and insecure residential status” (KNBS 2012, 4−5).<sup>12</sup> Table 1 reports household and housing characteristics by per capita consumption quartiles and informal status of their neighborhoods (see Table A1 for detailed summary statistics). Table A2 in Appendix A reports summary statistics for rental units in the city.

# **3-2. Methods**

_Job accessibility at the city level_ We use an urban accessibility metric to measure job accessibility in Nairobi (Avner and Lall 2016; Quirós and Mehndiratta 2015; Stewart and Zegras 2016). The model counts the number of reachable opportunities within a travel time isochrone. The most commonly used accessibility indicator is the share of opportunities that can be reached within a given time threshold. This normative choice has been recognized as meaningful (Bertaud 2014), although necessarily imperfect. The accessibility metrics, the job accessibility index (JAI), can be described by the following: where JAI� is the accessibility indicator for location i, O� represents the number of opportunities in location j, t�� is the travel time between location i and location j and t is a time threshold. �t�� �t�<sup>�</sup> in the numerator is a test that takes the value of either 0 or 1. In the latter case, opportunities in location _j_ can be reached and are added to the total of reachable opportunities. In the other case they are assigned the value 0. When averaged over the whole urban area ����JAI, localized accessibilities are weighted by population n�, to account for the fact that higher population densities are generally found in areas that benefit from good accessibility.

We also calculate the JAI for different groups of households based on their neighborhood status (informal or formal) and consumption quartiles. It is not clear a priori who benefits from better job accessibility between poor and non-poor households. Richer households may indeed choose to live at a further distance from the CBD and most job clusters, to enjoy larger houses—as is often assumed in urban economic theory—in exchange for longer commutes. They could however compensate longer distances with higher commuting speeds if they are equipped with cars and benefit from both good accessibility and larger dwellings. Yet, because only a tiny fraction of people commutes by car in Nairobi, even richer people may prioritize living closer to jobs. Poorer people are often constrained to live in informal settlements; so, their job accessibility depends on (a) the overall level of job accessibility in informal residential areas compared to formal areas and (b) the variation of job accessibility across informal neighborhoods. Thus, it is worth examining the JAI for different groups.

# _Hedonic models_

In the standard hedonic framework developed by Rosen (1974), the market prices of housing units represent the sum of expenditures in a bundle of characteristics that can be priced separately (see

> 12 The number of residents in Nairobi’s informal settlements varies depending on sources, and it is possible that the 2009 Census undercounted them. Even the population count of Kibera, the largest informal settlement in Nairobi, ranges from 170,070 to 270,000 (Lucci, Bhatkal, and Khan 2018).

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