A much preferable option to lift compliance above the current low levels would be to require a tax clearance certificate before any transfer, mortgage, or other encumbrance on a property can be registered. Such a measure treats property tax arrears as a high priority lien on the property and can be designed to act as implicit deferral of property dues, thus addressing concerns about property taxes reducing owners’ liquidity that have been raised in the literature (Brockmeyer _et al._ 2020). Another options to increase payment is to link tax payment explicitly to local service provision, including the possibility of withholding municipal services in case of non-payment. In systems that still rely on manual distribution of bills and a need to pay in person by queuing at government offices, allowing electronic billing and payment to reduce compliance cost (McCluskey _et al._ 2018).<sup>18</sup> The example of Nigeria where, with World Bank support, more than 30 states enumerated the majority of their urban properties based on satellite imagery in slightly more than a year and used this as a launchpad to improve services and make acquisition of documented land rights easier (Deininger _et al._ 2020a), in line with evidence from Ghana <mark>(Dzansi</mark> _<mark>et al.</mark>_ <mark>2022), DRC</mark> (Balan _et al._ 2020), and Senegal (Knebelman 2021). It also shows that creating a property tax roll can be a low-cost way of documenting use rights that can be shared with other public agencies (including land registries) to support planning and local service delivery with the possibility of either using such data as the basis for low-cost issuance of land rights or allowing tax payment receipts to mature into more substantive rights over time. Linking efforts to increase property taxation to reductions in registration or transaction fees could remove a major obstacle to establishment and maintenance of urban land registries, improve welfare, and yield political benefits if tax payment opens a path to acquiring real rights while at the same time creating enforcement capacity the lack of which has thus far bedeviled most efforts to increase property taxation in Africa.

# **4.2 Supporting compact and dense urban development**

Global data suggests that African cities are land-intensive, i.e. they consume lot of land and achieve density via crowding in slums rather than investment in height (Esch _et al._ 2023). This makes for sprawling cities with limited mobility (Peralta Quiros _et al._ 2019) where poor individuals can access only a limited number of jobs (Nakamura & Avner 2021). Land-intensive urban growth increases cities’ net <mark>carbon footprint,</mark><sup>19</sup> <mark>pollution exposure (</mark> Yao _et al._ 2021), and the cost of providing public services <mark>(Ashraf</mark> _<mark>et al.</mark>_ <mark>2021) including</mark> transport (Gendron-Carrier _et al._ 2022). Intra-city mobility increased knowledge spillovers and innovation in the US (Roche 2020) and is linked to higher economic growth in African cities (Brandily & Rauch 2020), suggesting that sprawling expansion may negatively affect cities’ growth potential.

> 18 In a randomized experiment in Zambia, SMS reminders increased payment significantly, especially for those on a network that allowed mobile payment. Effects were particularly large for payers outside the capital (Ali & Deininger 2021a).

> 19 <mark>Engineering studies that account for cities’</mark> total life-cycle GHG emissions suggest 7 to 27 floor buildings are optimal (Resch _et al._ 2016), though high density low rises may be preferable for stable populations (Pomponi _et al._ 2021). African cities have less than 2 floors on average.

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