We develop continuous-time models of capacity choice when demand fluctuates stochastically, and the firm's opportunities to expand or contract are limited. Specifically consider costs of investing or disinvesting that vary with time, or with the amount of capacity already installed. The firm's...

Capital investment decisions must recognize the limitations on the firm's ability later to sell off or expand capacity. This paper shows how opportunities for future expansion or contraction can be valued as options, how this valuation relates to the q-theory of investment, and how these options...

How does the sustainable level of consumption depend on productivity growth and the size and growth rate of the population? What is the effect of uncertainty over these growth rates? I address these questions using a model in which productivity and population growth are stochastic, and social...

A simple model of equity pricing is developed to address two related questions. First, to what extent can unanticipated changes in such"fundamental" variables as profitability, real interest rates, inflation, and the variance of returns account for the observed behavior of the stockmarket?...

Most explanations for the decline in share values over the past two decades have focused on the concurrent increase in inflation.This paper considers an alternative explanation: a substantial increase in the riskiness of capital investments. We show that the variance of firms' real gross...

There is a lot we know about climate change, but there is also a lot we don't know. Even if we knew how much CO2 will be emitted over the coming decades, we wouldn't know how much temperatures will rise as a result. And even if we could predict the extent of warming that will occur, we can say...

I use a simple SIR model, augmented to include deaths, to elucidate how pandemic progression is affected by the control of contagion, and examine the key trade-offs that underlie policy design. I illustrate how the cost of reducing the "reproduction number" R0 depends on how it changes the...

Climate policy is complicated by the considerable compounded uncertainties over the costs and benefits of abatement. We don't even know the probability distributions for future temperatures and impacts, making cost-benefit analysis based on expected values challenging to say the least. There are...

Any economic analysis of climate change policy requires some model that describes the impact of warming on future GDP and consumption. Most integrated assessment models (IAMs) relate temperature to the level of real GDP and consumption, but there are theoretical and empirical reasons to expect...