Source: authors’ elaboration based on Cattaneo, Nelson, & McMenomy (2021).

The ability to portray the URCAs of all urban centers in the world opens new possibilities to understand how rural–urban linkages may vary as a function of city size. For example, Cattaneo and co-authors (2021) describe the varying capacity of differing-sized cities to engage a proportionate rural population in their surroundings. This is visible in Figure 4, where the ratio of population outside the core of an urban center to its core is lowest for “mega” cities with a population of over 5 million and for towns of less than 50,000 people. Globally, this ratio is approximately four-times higher for intermediate cities, indicating that there is a relatively larger population share living in rural catchment areas of intermediate cities than for the largest cities or smallest towns. Indeed, as Partridge (2010) and Dijkstra and co-authors (2013, 2015) point out, intermediate-sized cities also have the advantage of generally being the fastest growing cities across the developed world. Figure 4 also indicates that small cities with populations ranging from 50,000 to 500,000 also sustain a substantial population in their catchment areas. The figure further reveals that the general inverted U-shaped profile of these ratios across the smallest towns to the largest cities is consistent regardless of average per-capita income levels.

The cause of this observed phenomenon warrants further investigation and could be tied to economic geography and the strategic location of smaller cities relative to varying-sized central places. Others note that intermediate-sized cities benefit from having sufficient agglomeration economies without the wide-scale congestion effects found in the largest cities (Partridge, 2010). Smaller and intermediate urban areas perform several essential functions, from market nodes for various services and goods, leading to increased nonfarm employment for their own population and that of their surrounding rural region. The different proportions of rural population to the core city identified in Figure 4 has implications for planning and development. For one, it supports the notion that faster growth in medium-size cities and relatively manageable congestion improves access to jobs, which in turn supports a larger rural population in their catchment areas.

In sum, this entire discussion of regions and the rural–urban continuum indicates more emphasis should be placed on small- and intermediate-sized cities, in developing smallholder agriculture, diversifying livelihoods, creating nonagricultural employment opportunities, and fostering broader development. To be sure, if there is a higher proportion of rural residents relying on services in intermediate-sized cities, this creates challenges for planning. While academics have recently recognized the importance of intermediate cities, national policy makers are often reluctant to target them given the outsized political power and attention received by the largest cities and capital cities (e.g., Dijkstra and co-authors, 2015). Yet, if smaller- and intermediate-sized cities do not garner sufficient public investment and infrastructure, then the potentially fastest-growing economic engines would be undermined.

# 4.3 Welfare and distributional challenges

One stylized fact about poverty is that it varies substantially across space, both in terms of share and density. Poverty rates are much larger in rural than in urban areas (Beegle & Christiaensen, 2019) and across urban areas they usually decrease with city size (Ferré, Ferreira, & Lanjouw, 2012). Poverty rates have further been reported to increase with distance from the urban center (Christiaensen & 18