The assignment of credit limits with a behaviour-scoring system

Received on 1 July 1991. Behaviour-scoring systems for authorizations enable the riskof a customer defaulting to be quantified. These risks mustbe incorporated into a credit strategy which assigns creditlimits and makes authorization decisions in the most effectivemanner. This paper introduces the concept of marginal risk whichhas proved a useful tool in defining credit limit strategiesfor a mail-order company. Behaviour scores for authorizations are similar to credit applicationscores in that they predict the overall risk of a customer defaulting.If a cut-off risk can be established, then the optimal strategywould appear to be to withhold credit for customers exceedingthis risk and to grant unlimited credit for the remainder (thisis analogous to application strategies). The notion of grantingunlimited credit is often commercially unacceptable (particularlyif customers are to be informed of their credit limits!) andso strategies which give all or nothing are of limited valueand need further refinement. In order to overcome this problem, the concept of marginal riskhas been devised. The marginal risk is the risk of the ‘last£’ of an account being defaulted. This reflectsthe fact that small-balance customers may well pay off theircurrent balance only to default on larger subsequent purchases.Although the overall risk of customers with a given behaviourscore defaulting is relatively constant, their marginal riskwill vary according to their outstanding balance. This paperexplores the relationships between marginal risk and overallrisk and between marginal risk and outstanding balance. A modelwhich summarizes these relationships is proposed, and contoursof equal marginal risk are built on the basis of this model.These contours provide strategies for allocating credit limitswhich are both practical and optimal for a well formulated cut-offrisk and which suggest that the probability of defaulting isnot the best criterion for allocating credit limits. The results of the application of this approach will be demonstrated.Some of the problems that have been overcome are discussed,as are some of the outstanding problems.     

POLITICS,ENVIRONMENT, AND FISHERIES: EMPIRICAL EVIDENCE FROM PACIFIC SALMON FISHERIES

Pacific salmon have always been a lucrative commodity in Alaska history. The primary contribution of this paper is to assess the effects of statewide policy changes such as the 1959 Alaska Statehood and the 1974 Limited Entry Act on the harvest of Pacific salmon in Alaska, controlling for changes in oceanic environmental conditions such as the Pacific Decadal Oscillation. An autoregressive distributed lag approach is employed to annual time‐series data for 1899–1996. We find that, while the 1974 Limited Entry Act has a significant effect on Alaska salmon harvests, the 1959 Alaska Statehood had little impact. In addition, the oceanic environment has an important determinant of long‐run Alaska salmon harvests.     

含三氟甲基1,2,3-三氮唑衍生物对蘑菇酪氨酸酶活性的抑制动力学(英文)

研究表明,含三氟甲基1,2,3-三氮唑衍生物(TF-TZ)对蘑菇酪氨酸酶具有很强的抑制性:不仅抑制单酚酶活性,而且对二酚酶活性也是可逆性抑制,其半抑制浓度IC50分别为30.4和34.5μmol.L-1,并且单酚酶延滞时间随着TF-TZ浓度增加而延长.TF-TZ对二酚酶的抑制为抛物线型竞争性抑制,表明一分子的酶可以和两分子的TF-TZ相结合,从而形成两种酶-抑制剂复合物:EI和EI2,其抑制常数分别为76.9和9.71μmol.L-1.紫外-可见光谱表明,TF-TZ和酶相互作用后产成特征的"肩峰",说明TF-TZ能够作用于酶的活性中心.     

PHOTOCHEMISTRY OF BENZOTHIAZOLE MODELS OF PHEOMELANIN

Abstract— The photochemistry of several 4-hydroxy- and 4-methoxybenzothiazoles has been investigated by laser flash photolysis. In aqueous solutions of pH3–12, the 4-hydroxybenzothiazole chromophore undergoes monophotonic photoionization to afford e^-_aq with quantum yields on the order of 0.06; no evidence for triplet species was obtained. The spectra and stability of the resultant free radicals were determined using pulse radiolysis. In contrast, triplet transients with life-times on the order of 8 mUs are readily observable upon irradiation of the 4-methoxybenzothiazole analog. Triplet sensitization experiments with the water-soluble carotenoid crocetin were employed to obtain the triplet extinction coefficients and subsequently the triplet quantum yields. The significance of these differences in photochemical behavior is discussed in relationship to the photochemistry and photobiology of the epidermal melanin pigment pheomelanin.     

EFFECTS OF DOMAIN SIZE ON THE PERSISTENCE OF POPULATIONS IN A DIFFUSIVE FOOD-CHAIN MODEL WITH BEDDINGTON-DeANGELIS FUNCTIONAL RESPONSE

ABSTRACT. A food chain consisting of species at three trophic levels is modeled using Beddington-DeAngelis functional responses as the links between trophic levels. The dispersal of the species is modeled by diffusion, so the resulting model is a three component reaction-diffusion system. The behavior of the system is described in terms of predictions of extinction or persistence of the species. Persistence is characterized via permanence, i.e., uniform persistence plus dissi-pativity. The way that the predictions of extinction or persistence depend on domain size is studied by examining how they vary as the size (but not the shape) of the underlying spatial domain is changed.     

Behavior in Repeated Prisoner's Dilemma Games with Shifted Outcomes Analyzed with a Statistical Learning Model

A fuzzy set theoretical framework is proposed for the analysis of sociometric structure characterized by vagueness of liking between individuals and a person's relative degree of belonging to a social group. Max‐min transitivity of a fuzzy relation is employed as a basic concept to examine the degree of liking and clustering in group structures. A distance model based on min‐max transitivity is also formulated as a special case of transitivity analysis. Other notions of transitivity such as the max‐product and the max‐* are also discussed. An empirical analysis is performed to examine the applicability of the proposed transitivity concepts. It appears that the current methodological construct provides a more appropriate perspective in the analysis of the group structure properties.