Three Essays On Asset Bubbles And Contagion Over Financial Networks

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Shen, Yue
asset bubble , contagion , networks , financial crisis
This thesis studies financial market stability by exploring asset bubbles and contagions over financial markets. First I construct a model where bubbles arise from a lack of common knowledge about the asset value among traders with private information, and I evaluate the effects of capital gain tax and transaction costs on bubbles. I find that capital gains tax has no effect on the size of the bubble when there is a perfect tax credit for capital losses, and the size of the bubble decreases in the tax when there is no tax credit. Therefore dealing with bubbles with capital gains tax not only requires imposing the tax, but also tightening the policies on tax credits. In a simplified bubble model, it can be shown that the model is equivalent to an auction, and bubbles arise for the same reason that bidding prices fail to reveal the true value in that auction. Several experiments on taxes and subsidies are devised to reduce or eliminate bubbles. Then I study the contagion of bankruptcy through downward price pressure among investors with overlapping portfolios. I calculate the probability of an extensive contagion and the expected bankruptcy rate during such a contagion. System-wide contagion happens only when the diversification of portfolios is in a certain range and, in the upper area of that range, the probability of a crisis may be small, but the spread of contagion can be extremely extensive.
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