A Proposal for a New Prescriptive Discounting Scheme: The Intergenerational Discount Rate

Cost-benefit analyses require comparing costs and benefits that occur at different points in time. Doing so, however, creates conflicts between short-term considerations — a discounting scheme has to be consistent with observed behaviours — and long-term ethical issues — a discounting scheme must not favour the current generation over future ones. To overcome this conflict, the present article proposes a prescriptive consumption discounting scheme that applies different discount rates (i) for various incomes in the lifetime of a unique individual and (ii) for various incomes that affect different individuals. Practically, any income flux is first discounted to the birth date of all individuals using a discount rate with a non-zero pure preference for the present; then these individual discounted values are discounted to the present with a discount rate with no preference for the present and finally summed up. The aim of this prescriptive discount rate is to be consistent with observed individual behaviour (descriptive discount rate) without favouring current generations. Consequences are discussed and compared with the UK Green Book and the Stern Review discounting schemes.Discount Rate, Intergenerational Equity

How economic growth and rational decisions can make disaster losses grow faster than wealth

Assuming that capital productivity is higher in areas at risk from natural hazards (such as coastal zones or flood plains), this paper shows that rapid development in these areas -- and the resulting increase in disaster losses -- may be the consequence of a rational and well-informed trade-off between lower disaster losses and higher productivity. With disasters possibly becoming less frequent but increasingly destructive in the future, average disaster losses may grow faster than wealth. Myopic expectations, lack of information, moral hazard, and externalities reinforce the likelihood of this scenario. These results have consequences on how to design risk management and climate change policies.Hazard Risk Management,Natural Disasters,Labor Policies,Insurance&Risk Mitigation,Economic Theory&Research

A Cost-Benefit Analysis of the New Orleans Flood Protection System

In the early stages of rebuilding New Orleans, a decision has to be made on the level of flood protection the city should implement. Such decisions are usually based on cost-benefit analyses. But in such an analysis, the results are contingent on a number of underlying assumptions and varying these assumptions can lead to different recommendations. Indeed, though a standard first-order analysis rules out category 5 hurricane protection, taking into account climate change and other human-related disruptions of environment, second-order impacts of large-scale disasters, possible changes in the discount rate, risk aversion and damage heterogeneity may make such a hurricane protection a rational investment, even if countervailing risks and moral hazard issues are included in the analysis. These results stress the high sensitivity of the CBA recommendation to several uncertain assumptions, highlight the importance of second-order costs and damage heterogeneity in welfare losses, and show how climate change creates an additional layer of uncertainty in infrastructure design that increases the probability of either under-adaptation (and increased risk) or over-adaptation (and sunk costs).Cost-Benefit analysis; Hurricane risk; New Orleans; Climate change

Adaptation to Climate Change: Do Not Count on Climate Scientists to Do Your Work

Many decisions concerning long-lived investments need to take into account climate change. But doing so is not easy for at least two reasons. First, due to the rate of climate change, new infrastructure will have to be able to cope with a large range of changing climate conditions, which will make design more difficult and construction more expensive. Second, uncertainty in future climate makes it impossible to directly use climate model outputs as inputs for infrastructure design, and there are good reasons to think that the needed climate information will not be available soon. Instead of optimizing based on the climate conditions projected by models, therefore, future infrastructure should be made robust to most possible changes in climate conditions. This aim implies that users of climate information must also change their practices and decision-making frameworks, for instance by adapting the uncertainty-management methods they currently apply to exchange rates or R&D outcomes. Five methods are examined: (i) introducing long-term prospective exercises; (ii) selecting 'no-regret' strategies; (iii) favouring reversible options; (iv) reducing decision time horizons; and (v) promoting soft adaptation strategies. I argue that adaptation strategies should not be assessed in an isolated context. In particular, it is essential to consider both negative and positive side-effects, including possible changes in future energy costs.

Accounting for Extreme Events in the Economic Assessment of Climate Change

Extreme events are one of the main channels through which climate and socio- economic systems interact. It is likely that climate change will modify their probability distributions and their consequences. The long-term growth models used in climate change assessments, however, cannot capture the effects of short-term shocks; they thus model extreme events in a very crude manner. To assess the importance of this limitation, a non-equilibrium dynamic model (NEDyM) is used to model the macroeconomic consequences of extreme events. Its conclusions are the following: (i) Dynamic processes multiply the extreme event direct costs by a factor 20; half of this increase comes from short-term processes; (ii) A possible modication of the extreme event distribution due to climate change can be responsible for significant GDP losses; (iii) The production losses caused by extreme events depend, with strong non-linearity, both on the changes in the extreme distribution and on the ability to fund the rehabilitation after each disaster. These conclusions illustrate that the economic assessment of climate change does not only depend on beliefs on climate change but also on beliefs on the economy. Moreover, they suggest that averaging short-term processes like extreme events over the five- or ten-year time step of a classical long-term growth model can lead to inaccurately low assessments of the climate change damages.Climate change, Extreme events, Economic impacts

A Cost-Benefit Analysis of the New Orleans Flood Protection System

In the early stages of rebuilding New Orleans, a decision has to be made on the level of flood protection the city should implement. Such decisions are usually based on cost-benefit analyses. But in such an analysis, the results are contingent on a number of underlying assumptions and varying these assumptions can lead to different recommendations. Indeed, though a standard first-order analysis rules out category 5 hurricane protection, taking into account climate change and other human-related disruptions of environment, second-order impacts of large-scale disasters, possible changes in the discount rate, risk aversion and damage heterogeneity may make such a hurricane protection a rational investment, even if countervailing risks and moral hazard issues are included in the analysis. These results stress the high sensitivity of the CBA recommendation to several uncertain assumptions, highlight the importance ofsecond-order costs and damage heterogeneity in welfare losses, and show how climate change creates an additional layer of uncertainty in infrastructure design that increases the probability of either under-adaptation (and increased risk) or over-adaptation (and sunk costs).

Behaviors and housing inertia are key factors in determining the consequences of a shock in transportation costs

This paper investigates the consequences of a sudden increase in transportation costs when households behaviors and buildings inertia are accounted for. A theoretical framework is proposed, capturing the interactions between behaviors, transportation costs and urban structure. It is found that changes in households consumption and housing choices reduce significantly the long-term adverse effects of a shock in transportation costs. Indeed, the shock translates, over the long-run, into a more concentrated housing that limits households utility losses and maintains landowners' income. But, because of buildings inertia, the shock leads first to a long transition, during which the adjustment is constrained by a suboptimal housing-supply structure. Then, households support larger losses than in the final stage, though lower than with no adjustment at all, and landowners experience a large decrease in their aggregate income and an important redistribution of wealth. Negative transitional effects grow as the shock becomes larger. Thus, behaviors and buildings inertia are key factors in determining the vulnerability to transportation price variability and to the introduction of climate policies. Our policy conclusions are that: (i) if a long-term increase in transportation costs is unavoidable because of climate change or resource scarcity, a smooth change, starting as early as possible, must be favored; and (ii) fast-growing cities of the developing world can reduce their future vulnerability to shocks in transportation costs through the implementation of policies that limit urban sprawl.City, Housing, Transportation

The Economics of Natural Disasters

Naturkatastrophe; Soziale Kosten; Messung; Prognoseverfahren; Theorie

Think Again: Higher Elasticity of Substitution Increases Economic Resilience

This paper shows that, counter-intuitively, a higher elasticity of substitution in model production function can lead to reduced economic resilience and larger vulnerability to shocks in production factor prices. This result is due to the fact that assuming a higher elasticity of substitution requires a recalibration of the production function parameters to keep the model initial state unchanged. This result has consequences for economic analysis, e.g., on the economic vulnerability to climate change.Substitution, Calibration, Constant Elasticity of Substitution, Shock

Compact or Spread-Out Cities: Urban Planning, Taxation, and the Vulnerability to Transportation Shocks

This paper shows that cities made more compact by transportation taxation are more robust than spread-out cities to shocks in transportation costs. Such a shock, indeed, entails negative transition effects that are caused by housing infrastructure inertia and are magnified in low-density cities. Distortions due to a transportation tax, however, have in absence of shock detrimental consequences that need to be accounted for. The range of beneficial tax levels can, therefore, be identified as a function of the possible magnitude of future shocks in transportation costs. These taxation levels, which can reach significant values, reduce city vulnerability and prevent lock-ins in under-optimal situations.Urban transportation, Housing, Inertia, Vulnerability, Transportation Taxation