numbers of workers and job opportunities, allows for sorting and matching between employers and employees<sup>5</sup> .

For these reasons, in this paper, we focus on metrics that capture accessibility to all employment opportunities in Nairobi as in Peralta Quiróz and Mehndiratta (2015). The purpose of the study is first to provide a diagnostic of the current situation in terms of access to jobs in Nairobi but also to initiate a discussion on ways in which residents’ accessibility can be improved. There are two main ways of enhancing accessibility: (a) build more or better transportation infrastructure, (b) help land uses evolve and adjust so as to allow for smooth connections between residential areas and opportunities. While the first possibility has triggered both a vast amount of literature and many investment projects, the second has received less attention. Transport projects are often necessary to ‘de-crowd’ cities, but improving the coordination of land uses throughout the urban area can probably achieve some of this goal without the extra costs of financing transport projects. There are typically two ways of changing land use patterns. The first one is to change the residential building stock for example by investing in more floor space in close proximity to opportunities or to transit stations. Advocates of compact city or Transit Oriented Development have focused on these options. The second is to consider the current building stock as fixed and to spatially allocate this capital so as to improve overall accessibility to opportunities. In this paper we investigate the second option and whether accessibility can be enhanced without additional investments. Developing economies are capital constrained so there is value in looking at whether or not it is possible to increase accessibility without additional financing. The assessment is based on the simulation of counterfactual scenarios of the location of jobs and households throughout the city without new investments in housing or transport infrastructure.

We derive a number of results from our analysis. The main result is that modifications to the spatial layout of Nairobi can increase the share of overall opportunities which can be accessed within a given time-frame. When commuters travel by foot or using the minibus network, the share of accessible jobs within an hour doubles from 11% to 21% and from 20% to 42% respectively. This result is important because it demonstrates that careful land use planning and zoning which is coordinated with transport infrastructure can lead to more integrated and efficient labor markets without large costs. Secondly, our results show that accessibility to employment is already a crucial determinant of the spatial layout of Nairobi, with people and employers choosing their locations so as to reduce commuting times and costs. Finally, we find that promoting equity in the access to jobs will result in mixed land use patterns and more even job-housing balance. Small labor markets, matching employment supply and demand locally, will however emerge at the expense of average aggregate accessibility and a fully integrated labor market which is conducive to the manifestation of agglomeration economies.

The paper is structured as follows: Section 2 provides background information about the current urban form in Nairobi County and the mobility of its residents. Section 3 presents the data sources used to investigate accessibility patterns, the distribution of residents and jobs as well as transport costs proxied by transport times for three transport modes: cars, matatus and pedestrians. Section 4 presents the results of the accessibility analysis for Nairobi as it is today. In particular it provides graphic evidence that accessibility is uneven geographically but also depending on whether residents have access to cars. Section 5 then introduces the main innovation of the paper which is to investigate

> 5 Although some authors (Niedzielski 2006; O Kelly and Lee 2005) have paid attention to worker and job characteristics so that the matching pattern yielded by solving the transportation problem is more realistic.

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