Essays on Financial Economics

This thesis addresses three topics in modern financial economics. In econometrics, we propose a consistent estimator for a model with both smooth structural changes and abrupt structural breaks. Our methodology is particularly well-suited for modern high frequency data. In market microstructure, we show that the traditional paradigm is no longer applicable in general, in light of recent technological evolution in trading and associated change in market behavior. In financial networks, we consider determinants of systematic risk that is due to the structure and stability of the network underlying the financial system. We propose a pricing factor that captures the diversification vs. contagion risk trade-off of the interconnectedness of the network.