The causes and consequences of the 2008 mortgage meltdown and 2020 COVID-19 crisis are quite different: the 2008 mortgage meltdown reflected infection of the financial system due to excess leverage and poor-quality mortgage loans, and the recent crisis reflects a substantial global economic shock to contain the viral outbreak of the coronavirus. Yet the financial and medical systems share many elements, such as opacity and interconnectedness as well as adequate buffers and reserves. We examine these themes as well as asset pricing, moral hazard (though it was at the root of the crisis only in the Great Recession), the consequences for government as a systemic actor, economic concentration, and capital market regulation in the two crises. In both crises, interventions in financial markets and disruptions in the housing market played important, but differing, roles. The recent crisis elucidates open questions about the foundation of financial economics and risk sharing.

In this article, we survey the literature that studies fixed-income trading rules and outcomes, including Treasury securities, corporate and municipal bonds, and structured credit products. We compare and contrast the microstructure and regulation of fixed-income markets with equity markets. We highlight the nature of over-the-counter trading in the face of search costs and the associated slow evolution of electronically facilitated intermediation. We discuss the databases available to study fixed-income microstructure, as well as measures and determinants of trading costs, and the important roles dealer networks and limited transparency play. We also highlight unresolved issues.