Faculty AI Research

A model for the systematic evaluation and management of a company's technological resources is proposed as a first step to developing an integrated corporate marketing-technology strategy. The proposed framework raises 4 issues: 1. technology identification, 2. technology additions, 3. technological commercialization, and 4. treatment of individual technologies as interdependent elements making up an integrated, coherent plan. The technological decision nexus involves decisions related to the firm's development and commercialization of its technology.

A new variable rate refining subdivision B4 for the solution of equations with piecewise linear homotopies and restart homotopies is described. The essential virtue of the subdivision B4 is that it offers vast latitude to the user. In particular, the parameters of B4 can be set so one restriction of B4 is that J3 triangulation and another restriction is the octahedral subdivision. More generally, full flexibility is available in the placement of local focal points, and perhaps most importantly, B4 permits the new capability of refining coordinates at variable and independent rates.

It is shown that an incumbent seller who faces a threat of entry into his or her market will sign long-tern contracts that prevent the entry of some lower-cost producers even though they do not preclude entry completely. Moreover, when a seller possesses superior information about the likelihood of entry, it is shown that the length of the contract may act as a signal of the true probability of entry.

Over the past 55 years returns on stock market indexes have on average been higher during the first half-month of calendar quarters 2 through 4 than at other times. Coincidentally, aggregate corporate earnings news arriving at the market during these half-month periods tends to be good, whereas earnings reports arriving later are more likely to convey bad news. In addition firms tend to publish bad-news earnings reports on Mondays, coincident with negative Monday effects in stock returns.

The perturbation generation rule of Suri (Ref. 1) is extended to cases where random variables are not generated by inversion. Conditions are given for the use of other methods. Infinitesimal perturbation analysis is shown to be compatible with common random number techniques in cases where finite-difference approximations are not.

We estimate labor demand equations derived from a (restricted variable) cost function in which "experience" on a technology (proxied by the mean age of the capital stock) enters "non-neutrally." Our specification of the underlying cost function is based on the hypothesis that highly educated workers have a comparative advantage with respect to the adjustment to and implementation of new technologies.

An analysis of the environments of leading manufacturing firms operating in the United States and in Australia produced a series of hypothesized differences in the strategies, organization structures, and market environments of firms in the two countries. Parallel hypotheses about differences between domestic Australian firms and subsidiaries of foreign multinationals operating in Australia were also developed. The hypotheses were by and large supported when tested on data obtained from leading corporations in the two countries.

A nonstationary Markov chain is weakly ergodic if the dependence on the state distribution on the starting state vanishes as time tends to infinity. A chain is strongly ergodic if it is weakly ergodic and converges in distribution. In this paper we show that the two ergodicity concepts are equivalent for finite chains under rather general (and widely verifiable) conditions. We discuss applications to probabalistic analyses of general search methods for combinatorial optimization problems (simulated annealing).

We characterize the sets of mimicking positions with returns that can serve in place of factors in an exact K-factor arbitrage-pricing relation for a set of N assets. All of the sets are K-dimensional nonsingular linear transformations of each other. We interpret three examples of such transformations and discuss empirical considerations. We provide conditions under which the mimicking positions can be expressed as portfolios, and we characterize the relation between mimicking portfolios and the minimum-variance frontier.

Based on observations made during an extensive study of police patrol operations in New York City, we examine the issues of the validity and utility of queueing models of service systems in which adaptive behavior by the (human) customers or servers is likely. We find that in addition to depending on the technical accuracy of its assumptions, the accuracy of such a model will also depend upon the level of managerial control of the system and adequacy of resources.

Evidence of excess volatilities of asset prices compared with those of market fundamentals is often attributed to speculative bubbles. This study demonstrates that bubbles could in theory lead to excess volatility, but it shows that certain variance bounds tests preclude bubbles as an explanation. The evidence ought to be attributed to model misspecification or inappropriate statistical tests. One important misspecification occurs if a researcher incorrectly specifies the time series properties of market fundamentals.

This paper examines Ricardian equivalence in a world in which taxes are not lump sum, but are levied on risky labor income. It shows that the marginal propensity to consume out of a tax cut, coupled with a future income tax increase, can be substantial under plausible assumptions. Indeed, the MPC out of a tax cut can be closer to the Keynesian value that ignores the future tax liabilities than to the Ricardian value that treats future taxes as if they were lump sum.

Most quantities of interest in discounted and undiscounted (semi-) Markov decision processes can be obtained by solving a system of functional equations. This paper derives bounds and variational characterizations for the solutions of such systems.

This paper considers a single-item, periodic-review inventory model with uncertain demands. In contrast to prior treatments of this problem we assume a finite production capacity per period. Assuming stationary data, a convex one-period cost function and a discrete demand distribution, we show (under a few additional unrestrictive assumptions) that a modified base-stock policy is optimal under the average-cost criterion; in addition, we characterize the optimal base-stock level.

This paper considers a single-item, periodic review inventory model with uncertain demands. We assume a finite production capacity in each period. With stationary data, a convex one-period cost function and a continuous demand distribution, we show (under a few additional unrestrictive assumptions) that a modified basic-stock policy is optimal under the discounted cost criterion, both for finite and infinite planning horizons. In addition we characterize the optimal base-stock levels in several ways.

We consider the problem of scheduling n jobs, each with a specific processing requirement, release time and due date on m uniform parallel machines. It is shown that a feasible schedule can be obtained by determining the maximum flow in a network, thus permitting the use of standard network flow codes. Using a specialized maximum flow procedure, the complexity reduces to O(tn³) operations when t is the number of distinct machine types.

This paper presents an allocation model for a perishable product, distributed from a regional center to a given set of locations with random demands. We consider the combined problem of allocating the available inventory at the center while deciding how these deliveries should be performed. Two types of delivery patterns are analyzed: the first pattern assumes that all demand points receive individual deliveries; the second pattern subsumes the frequently occuring case in which deliveries in multistop routes traveled by a fleet of vehicles. Computational experience is reported.

For a collection of agents with von Neumann-Morgenstern preferences, a price-independent income distribution, and identical probability beliefs, there exists a von Neumann-Morgenstern approximate aggregator. The risk tolerance of the approximate aggregator is equal to the sum of the individual agent risk tolerances at prices which yield constant, "risk-free," contingent consumption. The application of the approximate aggregator to standard asset pricing models in finance is discussed briefly.

Some companies consistently enjoy share prices that exceed book value. Such value creators range from giants like Coca-Cola Co., IBM, and Procter & Gamble to less-known small and medium-sized companies like Pall and Shoney's. Other enterprises trade below book value year after year, in both bear and bull markets. Many managers believe that these differences in price to book ratio do not stem from real differences in competitive performance but rather from the capriciousness of the stock market.

In the classical maximal flow problem, the objective is to maximize the supply to a single sink in a capacitated network. In this paper we consider general capacitated networks with multiple sinks: the objective is to optimize a general "concave" preference relation on the set of feasible supply vectors. We show that an optimal solution can be obtained by a marginal allocation procedure. An efficient implementation results in an adaptation of the augmenting path algorithm. We also discuss an application of the procedure for an investment company that deals in oil and gas ventures.

In many resource allocation problems, the objective is to allocate discrete resource units to a set of activities so as to maximize a concave objective function subject to upper bounds on the total amounts allotted to certain groups of activities. If the constraints determine a polymatroid and the objective is linear, it is well known that the greedy procedure results in an optimal solution. In this paper we extend this result to objectives that are "weakly concave," a property generalizing separable concavity.

Rational restrictions are derived for the values of American options on futures contracts. For these options, the optimal policy, in general, involves premature exercise. A model is developed for valuing options on futures contracts in a constant interest rate setting. Despite the fact that premature exercise may be optimal, the value of this American feature appears to be small and a European formula due to Black serves as a useful approximation. Finally, a model is developed to value these options in a world with stochastic interest rates.

Special algorithms have been developed to compute an optimal (s,S) policy for an inventory model with discrete demand and under standard assumptions (stationary data, a well-behaved one-period cost function, full backlogging and the average cost criterion). We present here an iterative algorithm for continuous demand distributions which avoids any form of prior discretization. The method can be viewed as a modified form of policy iteration applied to a Markov decision process with continuous state space. For phase-type distributions, the calculations can be done in closed form.

This paper analyzes the empirical behavior of stock-return volatilities prior to and subsequent to the ex-dates of stock splits. The evidence demonstrates rather unambiguously that there is, on the average, an approximately 30% "arbitrary" increase in the return standard deviations following the ex-date. The increase holds for both daily and weekly data, and it is not temporary. No explanatory confounding variables, such as institutional frictions affecting price observations, have been identified.

Let P be a polytope in Rⁿ containing the origin in its interior, and let P* be the algebraic dual polytope of P. Let Q Rⁿ x [0,1] be the (n+1)-dimensional polytope that is the convex hull of P x {1} and P* x {0}.

An extended series of economic studies has failed to find any statistically significant impact on national injury rates due to the OSHA. Two distinct explanations for this apparent failure of OSHA have been put forward in these studies. For the purposes of this study, the first of these explanations will be called the "noncompliance hypothesis" and the second will be labeled the "inefficiency hypothesis." The first of these hypotheses leads immediately to two dilemmas, which can only be resolved by expanding the range of issues considered in an analysis of OSHA.

In this paper, insider trading is viewed as a signal of managements' assessments of firms' future prospects and its information content is compared to that in managements' earnings forecasts. These forecasts are explicit statements of managements' assessments of future prospects. A number of measures of insider trading designed to capture the information aspect of trading are investigated.

The presence of traders with superior information leads to a positive bid-ask spread even when the specialist is risk-neutral and makes zero expected profits. The resulting transaction prices convey information, and the expectation of the average spread squared times volume is bounded by a number that is independent of insider activity. The serial correlation of transaction price differences is a function of the proportion of the spread due to adverse selection. A bid-ask spread implies a divergence between observed returns and realizable returns.

We consider a queueing system with two types of servers and two types of customers. General-use servers can provide service to either customer type while limited-use servers can be used only for one of the two. Though the apparent Markovian state space of this system is five-dimensional, we show that an aggregation results in an exact two-dimensional representation that is also Markovian. Matrix geometric theory is used to obtain approximations for the mean delay times and other measures of interest for each customer type.