While competition between firms producing substitutes is well understood, less is known about rivalry between complementors. We study the interaction between firms in markets with one-way essential complements. One good is essential to the use of the other but not vice versa, as arises with an...

We consider the provision of venture capital in a dynamic model with multiple research stages, where time and investment needed to meet each benchmark are unknown. The allocation of funds is subject moral hazard. The optimal contract provides for incentive payments linked to attaining the next...

This paper considers the financing of a research project under uncertainty about the time of completion and the probability of eventual success. The uncertainty about future success gradually diminishes with the arrival of addtional funding. The entrepreneur controls the funds and can divert...

This paper considers the financing of a research project under uncertainty about the time of completion and the probability of eventual success. We distinguish between two financing modes, namely relationship financing, where the allocation decision of the entrepreneur is observable, and arm's...

Our paper provides a complete characterization of leverage and default in binomial economies with financial assets serving as collateral. Our Binomial No-Default Theorem states that any equilibrium is equivalent (in real allocations and prices) to another equilibrium in which there is no...

During a crisis, developing countries regret having issued dollar denominated debt because they have to pay more when they have less. Ex ante, however, they may be worse off issuing local currency debt because the equilibrium interest rate might rise, making it more expensive for them to borrow....

We propose a theory of asset prices that emphasizes heterogeneous information as the main element determining prices of different securities. Our main analytical innovation is in formulating a model of noisy information aggregation through asset prices, which is parsimonious and tractable, yet...

We build a simple model of leveraged asset purchases with margin calls. Investment funds use what is perhaps the most basic financial strategy, called "value investing," i.e., systematically attempting to buy underpriced assets. When funds do not borrow, the price fluctuations of the asset are...

This is the graduation speech I gave on receiving an honorary doctorate at the University of Athens Economics and Business School. I talk about my Greek family, about how I got interested in economics, and then how in the 1990s I came to think about default, collateral, and leverage as the...

We show how the timing of financial innovation might have contributed to the mortgage bubble and then to the crash of 2007-2009. We show why tranching and leverage first raised asset prices and why CDS lowered them afterwards. This may seem puzzling, since it implies that creating a derivative...