hospital competition with soft budgets we study the incentives for hospitals to provide quality and expend cost reducing effort when their budgets are soft i e the payer may cover deficits or confiscate surpluses the basic set up is a hotelling model with two hospitals that differ in location and face demand uncertainty where the hospitals run deficits surpluses in the high low demand state softer budgets reduce cost efficiency while the effect on quality is ambiguous for given cost efficiency softer budgets increase quality since parts of the expenditures may be covered by the payer however softer budgets reduce cost reducing effort and the profit margin which in turn weakens quality incentives we also find that profit confiscation reduces quality and cost reducing effort first best is achieved by a strict no bailout and no profit confiscation policy when the regulated price is optimally set however for suboptimal prices a more lenient bailout policy can be welfare improving

prepayment and the valuation of mortgage backed securities this paper puts forward a valuation framework for mortgage backed securities rather than imposing an optimal value minimizing call condition we assume that at each point in time there exists a probability of prepaying this conditional probability depends upon the prevailing state of the economy to implement our valuation procedure we use maximum likelihood techniques to estimate a prepayment function in light of recent aggregate gnma prepayment experience by integrating this empirical prepayment function into our valuation framework we provide a complete model to value mortgagebacked securities given an optimal value minimizing call policy a mortgage should never be called when its market value is less than its call price similarly a mortgage should be called if it is worth more than its call price however mortgagors often call their loans when the prevailing refinancing rate exceeds the contract rate on the loan dunn and mcconnell 1981 in addition some mortgagors do not call their loans when the loan s contract rate exceeds the prevailing refinancing rate the purpose of this paper is to put forward a valuation framework for mortgagebacked securities consistent with these stylized facts associated with mortgage prepayments the mortgagor s prepayment decision is integral to our valuation framework however we do not impose an optimal value minimizing call condition to price these securities rather we assume that at each point in time there exists a probability of prepaying this conditional probability depending upon the prevailing state of the economy by integrating this prepayment function into our valuation framework we provide a complete model to value mortgage backed securities to implement our valuation procedures we estimate a prepayment function given recent gnma prepayment experience we follow green and shoven 1986 by using a proportional hazards model to estimate the influence of various explanatory variables or covariates on the mortgagor s prepayment decision distinct from green and shoven we explicitly model the effects of seasoning as well as investigating the influence of interest cost savings from refinancing in addition we also consider the effects of lagged refinancing rates heterogeneity

an equilibrium model of bond pricing and a test of market efficiency in two previous and related papers 3 4 the authors have reported the results of estimating a particular equilibrium model of bond pricing using quarterly data on canadian government bonds for the period 1964 to 1979 this paper reports the results of applying a similar model to the pricing of u s government bonds for the period 1958 1979 using data from the crsp government bond file the paper also extends the previous empirical analysis by evaluating the ability of the pricing model to detect underpriced and overpriced bonds the data reveal a strong relation between price prediction errors and subsequent bond returns

generalising interest rate duration with directional derivatives direction x and applications conventional or fisher weil duration is an ordinary derivative that measures the response of portfolio value to marginal parallel shifts in the term structure while other proposed measures are generally specific to particular interest rate processes in this paper we show that portfolio responses to arbitrary shifts in the term structure may be handled by the use of frechet or directional derivatives presenting a simple algorithm for the directional derivative of a fixed interest portfolio viewed as a set of cash flows for a given portfolio one can locate the most sensitive areas along the term structure by computing a function or profile direction x that gives the term structure movement to which the portfolio is most exposed immunisation techniques can be based on choosing ancillary assets that ensure that the portfolio directional derivative is zero or as close to zero as possible this generalises approaches based on factor models of the term structure the analysis is applied to both continuous and discrete time

differential taxation and the equilibrium structure of interest rates equilibrium coupon bond pricing relationships given differential taxation are derived under uncertainty assuming that both corporate and municipal bonds were originally issued at par but are currently selling at a discount the impact of differential taxation upon the term structure and coupon structure of interest rates is investigated while the tax structure of interest rates is uniquely characterized differential taxation substantially alters the prevailing equilibrium structure of interest rates

stochastic demand production responses and hospital costs this paper considers the production responses to demand uncertainty within the hospital sector it is noted that such responses have an impact on hospital cost structures an empirical model is specified estimation is undertaken on a sample of uk hospitals over the period 1993 1995 differentiating between hospital output which arises from uncertain demand emergency treatment and output considered to be predictable elective treatment the model estimates that the cost of an elective admission is approximately 45 of the cost of an emergency admission demand uncertainty imposes a direct cost equivalent to around 5 of the total cost of emergency admission

parameter estimation in stochastic scenario generation systems abstract scenario analysis offers an effective tool for addressing the stochastic elements in multi period financial planning models critical to any scenario generation process is the estimation of the input parameters of the underlying stochastic model for economic factors in this paper we propose a new approach for estimation known as the integrated parameter estimation ipe this approach combines the significant features of other well known estimation techniques within a non convex multiple objective optimization framework with the objective weights controlling the relative importance of the features we solve the non convex optimization problem using adaptive memory programming a variation of tabu search based on a short interest rate model using uk treasury rates from 1980 to 1995 the integrated approach compares favorably with maximum likelihood and the generalized method of moments we also evaluate performance with towers perrin s cap link scenario generation system

a nonlinear general equilibrium model of the term structure of interest rates abstract we derive and test an alternative closed form general equilibrium model of the term structure within the cox ingersoll and ross theoretical framework in which yields are nonlinear functions of the risk free rate we show that equilibrium bond prices and the risk free rate are not always inversely related and that bond risk need not be strictly increasing in maturity using hansen s generalized method of moments to obtain parameter estimates this nonlinear model outperforms the cox ingersoll and ross square root model in describing actual treasury bill yields for the 1964 1986 period

stochastic volatility option pricing this paper examines alternative methods for pricing options when the underlying security volatility is stochastic we show that when there is no correlation between innovations in security price and volatility the characteristic function of the average variance of the price process plays a pivotal role it may be used to simplify fourier option pricing techniques and to implement simple power series methods we compare these methods for the alternative mean reverting stochastic volatility models introduced by stein and stein 1991 and heston 1993 we also examine the biases in the black scholes model that are eliminated by allowing for stochastic volatility and we correct some errors in the stein and stein 1991 analysis of this issue empirical evidence on underlying asset prices and on their derivatives strongly suggests that asset price volatility is stochastic the pricing of options under this condition is therefore an important problem in this paper we study alternative option pricing methods that account for stochastic volatility we are particularly concerned with power series methods which we show to be quite accurate and easy to implement for alternative volatility specifications we point out their relation with recently proposed exact methods this permits a precise assessment of the approximation involved in the simple power series approach and of the impact of stochastic volatility on option prices following garman 1976 stochastic volatility option prices must satisfy a bivariate fundamental partial differential equation pde in the two state variables security price and volatility since volatility is not spanned by assets in the econ omy the volatility risk may not be eliminated by arbitrage methods therefore its market price explicitly enters into the pde the associated risk premium is owen graduate school of management vanderbilt university nashville tn 37203 and universita di siena facolta di scienza economiche e bancarie 53100 siena italy respectively part of this research was supported from a grant from the dean s fund and the financial markets research center at the owen school of management vanderbilt university some of this research was completed while roma was visiting the anderson graduate school of management ofthe university of california at los angeles we thank participants of the finance accounting and economics workshop at the owen school of management vanderbilt university for useful comments we appreciate the suggestions of roger huang craig lewis ron masulis and walter torous we thank joanne ball for editorial

valuation and analysis of collateralized mortgage obligations this study develops a model for the valuation of collateralized mortgage obligations cmos the model is based on a two factor model of the term structure of interest rates and embeds an empirically estimated mortgage prepayment function the model is used to analyze various cmo tranches including standard sequential pay fixed rate tranches planned amortization class pac tranches targeted amortization class tac tranches floating rate tranches interest only io and principal only po tranches z bonds and residuals the results of this analysis illustrate the sensitivity of the various tranches to differences in cmo structure changes in interest rates the characteristics of the underlying collateral and mortgage prepayments

exploring hospital production relationships with flexible functional forms this paper estimates a multiproduct variable cost function using data on a sample of california hospitals the results provide useful insights into the advantages and disadvantages of flexible functional forms for cost analysis the translog function appears to provide reasonable estimates of marginal costs when evaluated at or near the approximation point of the function the estimated function performs less satisfactorily however when evaluated outside this range the paper s results do not provide strong evidence of either ray scale economies or of weak cost complementarities there is some evidence however that the degree of scale economies may be underestimated

discretized reality and spurious profits in stochastic programming models for asset liability management in the literature on stochastic programming models for practical portfolio investment problems relatively little attention has been devoted to the question how the necessarily approximate description of the asset price uncertainty in these models influences the optimal solution in this paper we will show that it is important that asset prices in such a description are arbitrage free descriptions which have been suggested in the literature are often inconsistent with observed market prices and or use sampling to obtain a set of scenarios about the future we will show that this effectively introduces arbitrage opportunities in the optimization model for an investor who cannot exploit arbitrage opportunities directly because of market imperfections and trading restrictions we will illustrate that the presence of such arbitrage opportunities may cause substantial biases in the optimal investment strategy

hospital costs and excess bed capacity a statistical analysis this paper develops and estimates a cost model for u s hospitals analyzing the cost of excess bed capacity a new estimate is worth making for at least two reasons recent changes in the economic environment of hospitals have caused their utilization rates to fall sharply making previous estimates inaccurate second we employ econometric techniques not previously applied to this problem with estimation based on all short term community hospitals from 1979 89 our results based on conservative estimates of the average optimal occupancy rate indicate an annual cost of excess bed capacity of 17 2 billion in 1989 24 1 billion in 1991 and over 25 billion in 1993 copyright 1996 by mit press

the delivery option on forward contracts a comment livingston contends that short futures long cash traders can eliminate the potential costs of the quality option through use of a dynamic trading strategy it is proposed here that if this is possible then futures prices will never reach a stable equilibrium alternatively if livingston s argument is flawed then no risk free arbitrage opportunities are likely to be available to either short cash long futures or long cash short futures traders under such conditions futures prices will reach an equilibrium when the expected return and risk of each type position are equally attractive

are mortgage lenders guilty of the housing bubble a uk perspective existing theoretical models of house prices and credit rely on continuous rationality of consumers an assumption that has been frequently questioned in recent years meanwhile empirical investigations of the relationship between prices and credit are often based on national level data which is then tested for structural breaks and asymmetric responses usually with subsamples meen 1999 argues that local markets are structurally different from one another and so the coefficients of any estimated housing market model should vary from region to region we investigate differences in the price credit relationship for 12 regions of the uk markov switching is introduced to capture asymmetric market behaviours and turning points results show that credit abundance had a large impact on house prices in greater london and nearby regions alongside a strong positive feedback effect from past house price movements this impact is even larger in greater london and the south east of england when house prices are falling which are the only instances where the credit effect is more prominent than the positive feedback effect a strong positive feedback effect from past lending activity is also present in the loan dynamics furthermore bubble probabilities extracted using a discrete kalman filter neatly capture market turning points

the stochastic properties of term structure movements abstract the aim of this paper is to identify a stationary statistical model for treasury bill discount changes we find that the sample variance of discount changes are non stationary over short differencing intervals but stabilize as the intervals increase to quarterly or semi annual periods this result has important implications for pricing options and for analyzing the predictive properties of forward rates we show that the stochastic process structure leads to a downward revision in estimates of forward rate predictive power

hospital competition and quality with regulated prices we analyse the effect of competition on quality in hospital markets with regulated prices considering the effect of both introducing competition monopoly versus competition and increasing competition through either lower transportation costs increased substitutability or a higher number of hospitals with semi altruistic providers and a fairly general cost structure we show that the relationship between competition and quality is generally ambiguous in contrast to the received body of theoretical literature this is consistent with and potentially explains the mixed empirical evidence

bond price dynamics and options this paper provides a closed form preference free means of valuing a european call option written on a default free pure discount bond investors may not agree upon a theory of the term structure but they will necessarily agree on equilibrium option values further these equilibrium option values may be obtained without recourse to numerical approximation default free pure discount bond prices were posited to follow a non standardized transformed brownian bridge process this specification implicitly incorporates the terminal constraint that the price of a default free pure discount bond equal its face value at maturity contingent claim valuation necessarily involves consideration of terminal constraints on the value of financial securities the brownian bridge specification permits an appropriate means of incorporating a number of such constraints therefore while this paper has considered only the application of the brownian bridge process to the valuation of debt options the introduction of this process may provide for many further financial applications

uncertain demand the structure of hospital costs and the cost of empty hospital beds abstract in this paper we reformulate the theory of cost and production to take account of uncertain demand facing a firm in the reformulated theory the duality between cost and production no longer obtains and demand distribution parameters enter the cost function as well as the traditional outputs and input prices we then estimate a short run cost function for a hospital facing uncertain demand using data from a national sample of over 5000 hospitals for the years 1983 1987 the traditional cost model is strongly rejected in favor of the reformulated model this model is used to calculate the cost of empty hospital beds controlling for the effect of uncertain demand on the structure of hospital costs the cost of an empty hospital bed is calculated as 36 443 in 1987 dollars we estimate that a one percent decrease in the number of hospital beds would decrease hospital costs by slightly over one third of one percent increasing the occupancy rate from the average 1992 level 65 percent back to the average 1980 level 76 percent is estimated to save the average hospital over 2 million or 9 5 percent of costs

modeling the stochastic behavior of short term interest rates pricing implications for discount bonds abstract this paper models the stochastic behavior of short term interest rates and determines the correct specification of the drift and diffusion functions of the spot rate process a wide variety of one factor diffusion and two factor stochastic volatility models is compared in terms of their ability to capture the dynamics of interest rate volatility the empirical evidence on the one three and six month eurodollar deposit rates indicates that a new class of models with stochastic volatility is better than the single factor diffusion models in forecasting the future volatility of interest rate changes the paper extends the one factor bdt term structure model to a two factor setting and presents the pricing implications for discount bonds monte carlo simulation results for the implied yields of three and six month zero coupon bonds imply that incorporating the so called level and garch effects in volatility improves the pricing performance of the interest rate models

generational accounts for the united states an update abstract although relatively new generational accounting has been used in 26 countries to evaluate the generational stance of national fiscal policies generational accounting calculates the size of prospective net tax burdens and lifetime net tax rates that different generations face under current fiscal policy information that standard budget presentations do not reveal this method can also be used to calculate the policy changes required for achieving a generationally balanced and therefore sustainable fiscal policy that implies equal lifetime net tax rates on today s newborns and future generations those born after 1998 calculations made two years ago suggested a sizable generational imbalance in u s fiscal policy implying lifetime net tax rates on future generations that are 72 percent higher than those on newborns in 1995 since then unexpectedly strong growth in both gross domestic product gdp and the tax share of gdp has boosted revenues and slow growth in defense spending has reduced federal purchases as a share of gdp to a postwar low those developments augur federal budget surpluses for at least a decade and portend a corresponding reduction in the generational imbalance

shifting endpoints in the term structure of interest rates abstract this paper links the term structure to perceptions of monetary policy long horizon forecasts of short rates required by no arbitrage term structure models are heavily influenced by the endpoints or limiting conditional forecasts of the short rate process common assumptions that the short rate is mean reverting or contains a unit root are shown to generate unrealistic yield predictions failures occur because these assumptions inadequately account for historical shifts in market perceptions of the policy target for inflation this paper links endpoint shifts to agent learning about shifts in long term policy goals shifting endpoints in short rate processes significantly improve yield predictions

quality option profits switching option profits and variation margin costs an evaluation of their size and impact on treasury bond futures prices this paper provides empirical evidenee that the quality option in f bond futures is much less valuable than previously indicated in addition a dynamic trading strategy involving multiple switches of the cash bonds held in a long cash versus short futures position is shown to produce substantially greater profits than the single exercise of the quality op tion these findings suggest that the optimal management of long cash short futures positions is likely to involve dynamic trading strategies while passive strategies appear more appropriate for short cash long futures positions it is also shown that required variation margin payments are frequently large and may impact the profitability and risk of such positions to a greater extent than either of these options further evidenee is given indicating that observed t bond futures prices reflect an imputed value for the options and risks inherent in such positions

payment source and the cost of hospital care evidence from a multiproduct cost function with multiple payers abstract this study investigates the capacity of hospitals to vary the intensity of their services based on patients expected sources of payment while the concept of price discrimination by hospitals based on payer generosity cost shifting has been discussed extensively the notion that hospitals can adjust payer specific marginal costs to reflect differences in reimbursement policies has not been studied in depth to examine this issue this analysis employs a multiproduct cost function with hospital outputs defined as admissions by payment source controlling for the distribution and severity of illness casemix for each payer marginal costs of casemix adjusted discharges are obtained and compared for medicare medicaid private payers and a residual category that includes uncompensated care we find that indeed payer specific marginal costs generally reflect payer generosity

stochastic processes for interest rates and equilibrium bond prices default free bonds represent in essence money sold forward the investor gives dollars say to the government now in exchange for a contract which promises to pay with probability one a given number of dollars at maturity and possibly a stream of intermediate coupon payments prior to maturity only recently have financial economists begun to examine the pricing of those bonds in a portfolio context in that framework nominal liquidity premiums or risk premiums on long term default free bonds are attributable to uncertainty about taste technological and price level changes which may occur prior to maturity of the bonds and prior to each coupon payment if any to the extent that the investor is unable to diversify away that uncertainty there is a systematic risk attached to the marginal utility which he or she can derive from the use in consumption or investment of the dollar payoffs on the bonds in some term structure models the instantaneous or short term rate of interest denoted here as a function of time t by r t in nominal terms and r t in real terms can be taken as a sufficient statistic1 for the source of systematic uncertainty about the marginal utility of the proceeds to be derived from defaultfree bonds maturing beyond the next instant e g merton 1974 vasicek 1977 cox ingersoll and ross 1977 specific assumptions about tastes technology and utility functions lead to specific equilibrium stochastic processes for the instantaneous short term riskless rate and longer term bond prices which are modelled as functionally dependent upon maturity and that short term riskless rate if a closed form solution exists for the long term bond price as a function of maturity and the short term interest rate it will be conditional inter alia on the parameters of the stochastic process for that short term rate marsh 1981 proposed that the closed form solutions could be tested in terms of the restrictions implied cross sectionally on the parameters of the time series process for the returns or prices of longer term bonds each with a given term to maturity for an analogy outside the term structure literature think of the closed form solution given by black and scholes 1972 for the price of an option on a nondividend paying stock with lognormal price dynamics given the model the cross section of time series for the changes in prices for each of the several options written on the same stock are not unrestricted their dispersion is functionally linked to the same volatility parameter for the stock price thus the option model including

competition and quality in health care markets a differential game approach we investigate the effect of competition on quality in health care markets with regulated prices taking a differential game approach in which quality is a stock variable using a hotelling framework we derive the open loop solution health care providers set the optimal investment plan at the initial period and the feedback closed loop solution providers move investments in response to the dynamics of the states under the closed loop solution competition is more intense in the sense that providers observe quality in each period and base their investment on this information if the marginal provision cost is constant the open loop and closed loop solutions coincide and the results are similar to the ones obtained by static models if the marginal provision cost is increasing investment and quality are lower in the closed loop solution when competition is more intense in this case static models tend to exaggerate the positive effect of competition on quality