The outreach of macroprudential policies is likely limited in practice by imperfect regulation enforcement, whether due to shadow banking, regulatory arbitrage, or other regulation circumvention schemes. We study how such concerns affect the design of optimal regulatory policy in a workhorse model in which pecuniary externalities call for macroprudential taxes on debt, but with the addition of a novel constraint that financial regulators lack the ability to enforce taxes on a subset of agents. While regulated agents reduce risk taking in response to debt taxes, unregulated agents react to the safer environment by taking on more risk. These leakages undermine the effectiveness of macroprudential taxes but do not necessarily call for weaker interventions. A quantitative analysis of the model suggests that aggregate welfare gains and reductions in the severity and frequency of financial crises remain, on average, largely unaffected by even significant leakages.

Innovations and their adoption are the keys to growth and development. Innovations are less socially useful, but more profitable for the innovator, when they are adopted slowly and the innovator remains a monopolist. For this reason, rent-seeking, both public and private, plays an important role in determining the social usefulness of innovations. This paper examines the political economy of intellectual property, analyzing the trade-off between private and public rent-seeking. While it is true in principle that public rent-seeking may be a substitute for private rent-seeking, it is not true that this results always either in less private rent-seeking or in a welfare improvement. When the public sector itself is selfish and behaves rationally, we may experience the worst of public and private rent-seeking together.

We construct a competitive model of innovation and growth under constant returns to scale. Previous models of growth under constant returns cannot model technological innovation. Current models of endogenous innovation rely on the interplay between increasing returns and monopolistic markets. In fact, established wisdom claims monopoly power to be instrumental for innovation and sees the nonrivalrous nature of ideas as a natural conduit to increasing returns. The results here challenge the positive description of previous models and the normative conclusion that monopoly through copyright and patent is socially beneficial.