Staff Report 577
The Risk of Becoming Risk Averse: A Model of Asset Pricing and Trade Volumes
Published December 31, 2018
We develop a new general equilibrium model of asset pricing and asset trading volume in which agents’ motivations to trade arise due to uninsurable idiosyncratic shocks to agents’ risk tolerance. In response to these shocks, agents trade to rebalance their portfolios between risky and riskless assets. We study a positive question — When does trade volume become a pricing factor? — and a normative question — What is the impact of Tobin taxes on asset trading on welfare? In our model, economies in which marketwide risk tolerance is negatively correlated with trade volume have a higher risk premium for aggregate risk. Likewise, for a given economy, we ﬁnd that assets whose cash ﬂows are concentrated on states with high trading volume have higher prices and lower risk premia. We then show that Tobin taxes on asset trade have a ﬁrst-order negative impact on ex-ante welfare, i.e., a small subsidy to trade leads to an improvement in ex-ante welfare. Finally, we develop an alternative version of our model in which asset trade arises from uninsurable idiosyncratic shocks to agents’ hedging needs rather than shocks to their risk tolerance. We show that our positive results regarding the relationship between trade volume and asset prices carry through. In contrast, the normative implications of this speciﬁcation of our model for Tobin taxes or subsidies depend on the speciﬁcation of agents’ preferences and non-traded endowments.
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