Optimal patent length and breadth in an economy with creative destruction and non-diversifiable risk

In this paper, I examine the optimal patent shape in an economy in which R&D firms innovate and imitate, households face non-diversifiable risk and there is externality in production and R&D. With non-diversifiable risk, a household’s consumption and investment decisions are interlinked. This economy contains industries of two kinds: monopoly industries with an innovator only, and duopoly industries with an innovator and an imitator. I define patent length as the expected time in which an innovation is imitated, and patent breadth as the innovator’s profit share in an industry after a successful imitation. The government can control patent length by the requirements for accepting a substitute for a patented good, and patent breadth by imposing compulsory licensing and royalties for the patentee after a successful imitation. I show that the stronger the externality in production relative to R&D is, the slower the optimal growth rate, the larger the optimal proportion of duopoly industries, and the longer and narrower the optimal patent.     

The impact of prudence on optimal prevention

Summary. What are the determinants of the optimal level of effort to reduce the probability of a loss to occur? Whereas most of the literature on this question focused on risk aversion, we show that the concept of prudence (i.e., a positive third derivative of the utility function) is essential to answer this question. We explain in this paper that prudence and prevention tend to be opponents rather than allies contrary to the intuition attached to everyday language.Received: 7 November 2003, Revised: 3 August 2004, JEL Classification Numbers: D61, D81. Correspondence to: Christian Gollier     

Regulation of a Risk Averse Firm

We extend the Laffont–Tirole regulation model to the case of risk-averse firms. Our main results are:

• The impact of risk aversion is to shift the optimal contract toward a cost-plus contract.

• As compared with the risk-neutral case, distortions are greater and informational rents are smaller.

• For high levels of risk aversion, the optimal contract involves cost ceilings and the less efficient firms are bunched together.

Journal of Economic LiteratureClassification Numbers: D8, L5.     

Corporate insurance with optimal financial contracting

Summary. This paper attemps to rationalize the use of insurance covenants in financial contracts, and shows how external financing generates a demand for insurance by risk-neutral entrepreneurs. In our model, the entrepreneur needs external financing for a risky project that can be affected by an accident during its realization. Accident losses and final returns are private information to the firm, but they can be evaluated by two costly auditing technologies. We derive the optimal financial contract: it is a bundle of a standard debt contract and an insurance contract with franchise, trading off bankruptcy costs vs auditing costs. We then analyze how this optimal contract can be achieved by decentralized trading on competitive markets when insurance and credit activities are exogenously separated. With additive risks, the insurance contract involves full coverage above a straight deductible. We interpret this result by showing how our results imply induced risk aversion for risk-neutral firms. Received: December 14, 1998; revised version: August 11, 1999     

Designing social security - a portfolio choice approach

Public social security systems may provide diversification of risks to individuals’ life-time income. Capturing that a pay-as-you-go system (paygo) may be considered as a “quasi-asset”, we study the optimal size of the paygo system as well as the optimal split between funded and unfunded pension saving by means of a theoretical portfolio choice framework. A low-yielding paygo system can benefit individuals if it contributes to hedge other risks to their lifetime resources. Numerical calculations indicate that optimal social security systems should be at least partly paygo financed in many economies. The optimal magnitude of the paygo system depends on the specified risk concept as well as the stochastic properties of stock market returns and implicit paygo-returns.     

PERCEIVED ARSENIC‐RELATED MORTALITY RISKS FOR SMOKERS AND NON‐SMOKERS

Prolonged ingestion of arsenic in drinking water can increase the risks of dying of lung and bladder cancer, particularly for smokers. In a survey of arsenic hotspots in the United States, we elicited individuals' subjective mortality risks related to the presence of arsenic in drinking water. Using this data, we address whether smokers perceive mortality risks from this source differently from non‐smokers. We find that those who have smoked at some point in their life have significantly higher perceived arsenic mortality risks than those who have never smoked, on average. We also find that the sample group of current smokers has higher average perceived arsenic mortality risks than those who have quit smoking. We model the decision to treat water for arsenic and find some evidence that current smokers are less likely to engage in this mitigating behavior than are ex‐smokers or non‐smokers even though their perceived risk is higher. We infer that smokers are either less risk averse or have a higher rate of time preference than non‐smokers and ex‐smokers. (JEL I0, D81, Q53)     

A general model of insurance under adverse selection

Summary. This paper considers optimal insurance schemes in a principal-agent multi-dimensional environment in which two types of risk averse agents differ in both risk and attitude to risk. Risk corresponds to any pair of distribution functions (not necessarily ordered by any of the usual dominance relations) and attitudes to risk are represented by any pair of non-decreasing and concave utility functions (not necessarily ordered by risk aversion). Results obtained in one-dimensional models that considered these effects separately and under more restricted conditions, are preserved in the more general set-up, but some of the questions we study can only be posed in the more general framework. The main results obtained for optimal insurance schemes are: (i) Insurance schemes preserve the order of certainty equivalents; consequently, the latter constitute a one-dimensional representation of types. (ii) Agents with the lower certainty equivalent are assigned full insurance. Partial insurance assigned to the others may entail randomization. (iii) Partially insured positions are an increasing function of the ratios of the probabilities that the two types assign to the uninsured positions. Most of these properties are preserved when, due to competition or other reasons, the insured certainty equivalents can not be set below pre-determined levels. Received: January 13, 1998; revised version: October 10, 1998     

An Optimal Auction for Complements

This paper considers the optimal selling mechanism for complementary items. When buyers are perfectly symmetric, the optimal procedure is to bundle the items and run a standard auction. In general, however, bundling the items is not necessarily desirable, and the standard auctions do not maximize revenue. Moreover, the optimal auction allocation may not be socially efficient since the auction must discriminate against bidders who have strong incentives to misrepresent their true preferences.Journal of Economic LiteratureClassification Number: D44.     

k-Price Auctions

In this paper we analyze the equilibria structure of k-price auctions, k ≥ 3, under the independent-private-value assumption. We discuss agents with an arbitrary attitude toward risk. That is, agents may be risk averse or risk seeking, or they may have an alternating attitude toward risk. We provide a characterization of a continuous symmetric equilibrium, prove that there exists at most one such equilibrium, and show that every such equilibrium is differentiable and increasing. We also show some additional general properties of the equilibrium strategies in these auctions. Journal of Economic Literature Classification Numbers: C72, C73, D83.     

The optimality of nominal contracts

Summary. This paper presents a model in which agents choose to use money as a medium of exchange, a means of payment, and a unit of account. The paper defines conditions under which nominal contracts, promising future payment of a fixed number of units of fiat money, prove to be the optimal contract form in the presence of either relative or aggregate price risk. When relative prices are random, nominal contracts are optimal if individuals have ex ante similar preferences over future consumption. When the aggregate price level is random, whether from shocks to the money supply or aggregate output, nominal contracts (perhaps coupled with equity contracts) lead to optimal risk-sharing if individuals have the same degree of relative risk aversion. Finally, nominal contracts may be optimal if the repayment of contracts is subject to a binding cash-in-advance constraint. In this case, a contingent contract increases the risk of holding excessive cash balances. Received: March 29, 1996; revised version: February 25, 1997     

Bank capital requirements and mandatory deferral of compensation

We analyze the interplay of capital requirements and mandatory deferral of compensation in reducing banks’ risk taking incentives. Two heterogenous banks fund uncorrelated projects with fully diversifiable risk or correlated projects with systematic risk. One of both banks can identify project types and is superior at managing risks. If projects are in abundant supply, full mandatory deferral of compensation is optimal as it allows a larger banking sector without increasing the default risk. With limited supply of projects, deferred compensation may misallocate risky projects to the bank that is inferior at managing risks, so that early compensation may be optimal.     

Optimal saving in the presence of two risks

We examine optimal saving in the presence of two small risks: income risk and a background risk. First, we compute the necessary and sufficient condition for a positive precautionary saving, showing that it depends on two terms capturing respectively the direct effect of income risk and the interaction between the two risks. Second, we examine the necessary and sufficient condition for a positive extra-saving due to the contemporaneous presence of the two risks. We show that this condition also depends on a term capturing the direct effect of background risk and that it can hold independently of the previous one.      

Insurance with Frequency Trading: A Dynamic Analysis of Efficient Insurance Markets

This paper extends existing insurance results on the type of insurance contracts needed for insurance market efficiency to a dynamic setting. It introduces continuously open markets that allow for more efficient asset allocation. It also estimates the role of preferences and endowments in the classification of risks, which is done primarily in terms of the actuarial properties of the underlying risk process. The paper further extends insurability to include correlated and catastrophic events. Under these very general conditions the paper defines a condition that determines whether a small number of standard insurance contracts (together with aggregate assets) suffice to complete markets or one needs to introduce such assets as mutual insurance. Journal of Economic Literature Classification Numbers: D81, D99, G11.     

Methods for estimating optimal Dickson and Waters modification dividend barrier

In applications of collective risk theory, complete information for the distribution of individual claims amount is often unknown, but reliable estimates of its first few moments may be available. Dickson and Waters [Dickson, D.C.M. and Waters, H.R., (2004) Some optimal dividends problems, Astin Bulletin, 34, 49–74.] pointed out that shareholders should be liable to cover the deficit at ruin. Thus, they considered b the level of the barrier that maximizes the expectation of the difference between the discounted dividends until ruin and the discounted deficit at ruin. For such a situation, this paper develops methods for estimating the Dickson–Waters modification for the optimal dividend barrier b with the expectation of discounted penalty at ruin. In particular, two De Vylder approximations are explained, and the diffusion approximation for the expectation of discounted penalty at ruin is examined. For several claim amount distributions, the approximate values are compared numerically with exact values.     

Reserve Prices without Commitment

When potential bidders in an auction have to incur a cost to prepare their bids and thus to learn their valuations, imposing a reserve price and announcing that in case no bid is submitted there will be another auction without a reserve price is both revenue and welfare improving. Reserve prices that induce less than maximum entry in the first auction may be optimal. Also, entry fees are not necessarily better instruments than reserve prices.Journal of Economic LiteratureClassification Number: D44.     

DO PSYCHOLOGICAL SHOCKS AFFECT FINANCIAL RISK TAKING BEHAVIOR? A STUDY OF U.S. VETERANS

Traditional economic theories assume that individuals are endowed with certain risk preferences that are unaltered by experiences. However, recent evidence indicates that macroeconomic shocks do have an effect on an individual's willingness to take financial risks. In the context of investment decisions, we examine empirically whether an individual's risk preferences are affected by other types of traumatic life experiences. Using a unique proprietary data set, we investigate whether personal traumatic experiences—such as the combat experiences of veterans—have long‐term effects on financial risk‐taking behavior. We find that having experienced combat decreases the probability of investing in risky assets. Key policy implications are noted. (JEL G11, D14)     

Private Sector Involvement in Infrastructure Projects

There has been little systematic discussion of the issues associated with private involvement in infrastructure. Analysis of the relative performance of the private and public sector in different phases of infrastructure provision suggests that, in most cases, the private sector will be most efficient in the construction phase but the public sector will be best equipped to handle the risks associated with ownership. The situation is less clear-cut with respect to operation—a mixture in which core operations are undertaken by the public sector owner with peripheral operations being contracted out may be optimal in many cases.     

Background risk and the demand for state-contingent claims

Summary. We consider the demand for state-contingent claims, in the presence of an independent zero-mean, non-hedgeable background risk. An agent is defined to be generalized risk averse if he/she chooses a demand function for contingent claims with a smaller slope everywhere, given a simple increase in background risk. We show that the conditions for standard risk aversion, that is positive, declining absolute risk aversion and prudence, are necessary and sufficient for generalized risk aversion.Received: 13 February 2002, Revised: 10 February 2003, JEL Classification Numbers: D52, D81, G11. Correspondence to: Guenter FrankeWe are grateful to Louis Eeckhoudt, Christian Gollier, Harris Schlesinger and an unknown referee for valuable comments.     

Risk aversion and incentive compatibility with ex post information asymmetry

Summary. The paper extends Diamond's (1984) analysis of financial contracting with information asymmetry ex post and endogenous “bankruptcy penalties” to allow for risk aversion of the borrower. The optimality of debt contracts, which Diamond obtained for the case of risk neutrality, is shown to be nonrobust to the introduction of risk aversion. This contrasts with the costly state verification literature, in which debt contracts are optimal for risk averse as well as risk neutral borrowers. Received: December 7, 1998; revised version: June 9, 1999     

Efficiency and options on the market index

Summary. In a static exchange economy, when all the endowments are issued as securities on a stock exchange, Pareto optimal allocations may be reached by trading options on the market index (see Breeden and Litzenberger (1978)). We extend this result when some of the risks cannot be exchanged on the market. Options on an appropriate index, which typically differs from the market index, depending on the correlation of the non-tradable risks with the exchanged securities, are still an appropriate tool to support a (constrained) efficient equilibrium. This suggests that the recent development of derivatives based on interest rates may be an efficient way to reach a Pareto optimal allocation of risks. Received: June 16, 1997; revised version: July 25, 1997