Against the backdrop of increased international mobility of individuals, this paper addresses a central tax challenge in this context: the taxation of capital gains. Because capital gains taxation is generally realization-based, taxpayer mobility prior to realization can erode countries’ taxing rights. In response, both the academic literature and policymakers have considered the use of exit taxes on accrued, unrealized gains. Drawing on economic approaches to formula apportionment and tax averaging, as well as legal concepts from tax and public policy, this paper develops and evaluates a novel framework for capital gains taxation: Cross-Border Capital Gains Taxation (CBCGT). The model harmonizes capital gains taxation through cross-border realization-based averaging and intertemporal apportionment. Thereby it balances competing principles of realization-based taxation and accrual-based allocation. The proposal aims to improve international tax policy, and to this end, the paper conducts a legal analysis of its potential application, using the EU as a case study.

Deployment subsidies for nascent technologies have moved to the forefront of climate action, industrial policy, and geoeconomics. To limit the substantial fiscal costs of such programs, policymakers routinely employ subsidy schedules that are nonlinear in the quantity agents deploy. However, nonlinearities can threaten a program's deployment goals because agents may respond to them at the intensive margin by reducing deployed quantity and at the extensive margin by ceasing participation. This paper characterizes optimal nonlinear subsidy schemes in which a principal trades off the benefits from deployment with its budgetary costs. Theoretically, it shows that nonlinearities are optimal only if adopters' participation responses are heterogeneous along the subsidy schedule. Yet, early-stage technologies typically exhibit limited heterogeneity in this dimension. As a consequence, the optimal subsidy rate is close to constant over a wide range of the schedule. A quantitative analysis of the canonical German rooftop-solar program demonstrates the theoretical findings.

Many resource-rich countries have raised tax rates on mining extraction over the past two decades, amid surging demand for minerals. Using a global firm-level panel of mining exploration and production from 1997 to 2024, combined with a newly compiled dataset of statutory tax rates, I find that higher taxes leave production from existing mines unchanged but sharply reduce exploration: a one-percentage-point increase in sales royalties lowers exploration expenditures by 3 to 4 percent, with no significant effect on short-run output. Event studies around the four largest mining tax reforms of the past two decades - South Africa (2010), Ghana (2012), Mexico (2014), and the DRC (2018) - confirm this result. Affected firms gradually relocate exploration abroad, leaving global exploration unchanged in the long run. These findings document a time-inconsistency problem in resource taxation: governments can capture short-run rents from immobile production but erode their long-run tax base by deterring discovery.