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Report
How Deadly is COVID-19? Understanding the Difficulties with Estimation of its Fatality Rate
To understand how best to combat COVID-19, we must understand how deadly is the disease. There is a substantial debate in the epidemiological literature as to whether the fatality rate is 1% or 0.1% or somewhere in between. In this note, I use an SIR model to examine why it is difficult to estimate the fatality rate from the disease and how long we might have to wait to resolve this question absent a large-scale randomized testing program. I focus on uncertainty over the joint distribution of the fatality rate and the initial number of active cases at the start of the epidemic around January ...
Report
On the optimal choice of a monetary policy instrument
The optimal choice of a monetary policy instrument depends on how tight and transparent the available instruments are and on whether policymakers can commit to future policies. Tightness is always desirable; transparency is only if policymakers cannot commit. Interest rates, which can be made endogenously tight, have a natural advantage over money growth and exchange rates, which cannot. As prices, interest and exchange rates are more transparent than money growth. All else equal, the best instrument is interest rates and the next-best, exchange rates. These findings are consistent with the ...
Working Paper
Time-varying risk, interest rates and exchange rates in general equilibrium
Time-varying risk is the primary force driving nominal interest rate differentials on currency-denominated bonds. This finding is an immediate implication of the fact that exchange rates are roughly random walks. We show that a general equilibrium monetary model with an endogenous source of risk variation?a variable degree of asset market segmentation?can produce key features of actual interest rates and exchange rates. The endogenous segmentation arises from a fixed cost for agents to exchange money for assets. As inflation varies, the benefit of asset market participation varies, and that ...
Report
Money and interest rates with endogeneously segmented markets
This paper analyses the effects of open market operations on interest rates in a model in which agents must pay a fixed cost to exchange assets and cash. Asset markets are endogenously segmented in that some agents choose to pay the fixed cost and some do not. When the fixed cost is zero, the model reduces to the standard one in which persistent money injections increase nominal interest rates, flatten the yield curve, and lead to a downward-sloping yield curve on average. In contrast, if markets are sufficiently segmented, then persistent money injections decrease interest rates, steepen or ...
Working Paper
On the optimality of transparent monetary policy
We analyze the optimal design of monetary rules. We suppose there is an agreed upon social welfare function that depends on the randomly fluctuating state of the economy and that the monetary authority has private information about that state. We suppose the government can constrain the policies of the monetary authority by legislating a rule. In general, well-designed rules trade-off the need to constrain policymakers from the standard time consistency problem arising from the temptation for unexpected inflation with the desire to give them flexibility to react to their private information. ...
Report
Behavior and the Transmission of COVID-19
We show that a simple model of COVID-19 that incorporates feedback from disease prevalence to disease transmission through an endogenous response of human behavior does a remarkable job fitting the main features of the data on the growth rates of daily deaths observed across a large number countries and states of the United States from March to November of 2020. This finding, however, suggests a new empirical puzzle. Using an accounting procedure akin to that used for Business Cycle Accounting as in Chari et al. (2007), we show that when the parameters of the behavioral response of ...
Report
There Is No Excess Volatility Puzzle
We present two valuation models which we use to account for the annual data on price per share and dividends per share for the CRSP Value-Weighted Index from 1929 to 2023. We show that it is a simple matter to account for these data based purely on a model of variation over time in the expected ratio of dividends per share to aggregate consumption under two conditions. First, investors must receive news shocks regarding the expected ratio of dividends per share to aggregate consumption in the long run. Second, the discount rate used to evaluate the impact of this news on the current price per ...
Report
Innovation, firm dynamics, and international trade
We present a general equilibrium model of the response of firms' decisions to operate, innovate, and engage in international trade to a change in the marginal cost of international trade. We find that, although a change in trade costs can have a substantial impact on heterogeneous firms' exit, export, and process innovation decisions, the impact of changes in these decisions on welfare is largely offset by the response of product innovation. Our results suggest that microeconomic evidence on firms' responses to changes in international trade costs may not be informative about the implications ...
Working Paper
Putty-clay capital and energy
We evaluate the ability of models with putty-clay capital and stochastic energy prices to account for the dynamics of energy use and output. Economists have noted a close relationship between changes in the price of energy and changes in output. Moreover, they have documents that this relationship is asymmetric: energy price increases are associated with large output charges while energy prices decreases are associated with small output changes. Finally, following energy price changes, energy use adjusts slowly over time. Standard models with putty-putty capital fail to reproduce the features ...
Report
The advantage of transparency in monetary policy instruments
Monetary policy instruments differ in tightness - how closely they are linked to inflation - and transparency - how easily they can be monitored. Tightness is always desirable in a monetary policy instrument; when is transparency? When a government cannot commit to follow a given policy. We apply this argument to a classic question: Is the exchange rate or the money growth rate the better monetary policy instrument? We show that if the instruments are equally tight and a government cannot commit to a policy, then the exchange rate's greater transparency gives it an advantage as a monetary ...