programming algorithm to predict an adjusted house price index for arbitrary spatial units from repeated cross-sections of geocoded micro data has been used to generate a panel of German property prices and rents that is unprecedented in its spatial coverage and detail. It provides price and rent indices for residential and commercial properties while also raising questions for follow-up research (Ahlfeldt _et al._ 2023).

Based on such experiences, the methodology for property valuation has been standardized (Diewert et al. 2020), allowing quick transfers to other contexts. In Lithuania, assessed property values more than quadrupled as a result of adopting and gradually refining the mass valuation system (Almy 2015) that is now at the core of a private sector–driven registry system that provides many ancillary benefits (Grover et al. 2017). Most African countries still require valuation of all property by a licensed valuer (Franzsen and McCluskey 2017), despite the high cost and potential arbitrariness. Using CAMA for residential properties and focusing scarce valuation capacity on commercial property has proven to be a more viable way to ensure buoyancy by allowing frequent revaluation.

_Credible enforcement and minimal exemptions._ Reducing compliance costs, for example, via e-billing and mobile payment options (McCluskey et al. 2018), can help increase property tax collection.<sup>9</sup> To improve enforcement, treating property tax arrears as a high priority lien on the property or requiring tax clearance before any transfer, mortgage, or other encumbrance can be registered on a property seems to be a low-cost but feasible option. By implicitly deferring tax payment until the point when the asset is liquidated, this can also address concerns about negative liquidity effects of property taxes, especially on seniors who, if they are unwilling to move, might have to reduce consumption to pay increasing property taxes levied on the assessed value of their home (Brockmeyer et al. 2020).<sup>10</sup> Tax codes often contain ample exemptions, including for owner-occupied properties or pensioners that are difficult to justify from an economic perspective (Englund 2003) as all of these consume the local services supplied using property tax proceeds. These can significantly reduce tax revenue (Balan et al. 2020) and yield (Ali, Deininger and Wild 2020) and may negatively affect governance, efficiency of land use, and perceived fairness of the system. While public disclosure of tax information or social recognition have often increased compliance (Slemrod _et al._ 2022), public disclosure in Uganda reduced compliance, consistent with the notion that individuals overestimate compliance levels and, once they learn the truth, stop complying not to be taken advantage of (Regan and Manwaring 2023).<sup>11</sup>

> 9 In a randomized experiment in Zambia, text message reminders significantly increased payment, especially for those on a network that allowed mobile payment. Effects were particularly large for payers outside the capital (Ali and Deininger 2021).

> 10 As housing wealth is illiquid, changes in wealth, for example, via housing booms or property tax liabilities, can trigger large wealth effects and, through these, affect consumption or economic activity. In Italy, tax increases on the main dwelling led to large expenditure cuts among mortgagors who hold low liquid wealth despite owning sizable illiquid assets (Surico and Trezzi 2019). In the United States, property tax limits reduced female labor force participation by 0.7 to 1.4 percentage points during the 2005–06 housing boom (Liu and Yang 2020).

> 11 Reminders to pay taxes were effective if they were credible (Castro and Scartascini 2015) or described the effects of nonpayment (Chirico et al. 2017). Beliefs about the ability of the authorities to penalize defaulters also affected truthful declaration of other taxes (Lopez-Luzuriaga and

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