Endogenous Sampling in Duration Models

This paper considers the problem of endogenous sampling in the duration model. This is an important problem in the duration analysis of bank failures and loan defaults because it is common for the researchers in these areas to use only the default sample or non-default sample or both at a certain ratio, rather than using a random sample. The properties of endogenous sampling have been considered in various models, notably in qualitative response models, but not in duration models as far as I am aware. In this paper, I obtain the asymptotic distribution of the endogenous sampling maximum likelihood estimator and compare it with that of the random sampling maximum likelihood estimator and indicate when efficiency gain may result. I also show that the random sampling maximum likelihood estimator is inconsistent if the data are collected by endogenous sampling.

Endogenous Sampling and Matching Method in Duration Models

Endogenous sampling with matching (also called gmixed samplingh) occurs when the statistician samples from the non-right- censored subset at a predetermined proportion and matches on one or more exogenous variables when sampling from the right-censored subset. This is widely applied in the duration analysis of firm failures, loan defaults, insurer insolvencies, and so on, due to the low frequency of observing non-right-censored samples (bankrupt, default, and insolvent observations in respective examples). However, the common practice of using estimation procedures intended for random sampling or for the qualitative response model will yield either an inconsistent or inefficient estimator. This paper proposes a consistent and efficient estimator and investigates its asymptotic properties. In addition, this paper evaluates the magnitude of asymptotic bias when the model is estimated as if it were a random sample or an endogenous sample without matching. This paper also compares the relative efficiency of other commonly used estimators and provides a general guideline for optimally choosing sample designs. The Monte Carlo study with a simple example shows that random sampling yields an estimator of poor finite sample properties when the population is extremely unbalanced in terms of default and non-default cases while endogenous sampling and mixed sampling are robust in this situation.Duration models; Endogenous sampling with matching; Maximum likelihood estimator; Manski-Lerman estimator; Asymptotic distribution

The Maximum Likelihood Stage Least Squares Estimator in the Nonlinear Simultaneous Equations Model

The consistency and the asymptotic normality of the maximum likelihood estimator in the general nonlinear simultaneous equation model are proved. It is shown that the proof depends on the assumption of normality unlike in the linear simultaneous equation model. It is proved that the maximum likelihood estimator is asymptotically more efficient than the nonlinear three-stage least squares estimator if the specification is correct, However, the latter has the advantage of being consistent even when the normality assumption is removed. Hausrnan' s instrumental-variable-interpretation of the maximum likelihood estimator is extended to the general nonlinear simultaneous equation model.

Spontaneous complete necrosis of hepatocellular carcinoma caused by feeding vessel occlusion outside the tumour capsule

A 64-year-old man began treatment for chronic hepatitis C with peg-interferon and ribavirin. His hepatitis C virus ribonucleic acid (HCV-RNA) results turned negative. Just after the treatment, a computed tomography (CT) scan revealed a hypovascular mass in the segment 8. We performed a right hemihepatectomy as HCC. Upon macroscopic examination, the tumour was yellow and firm with a fibrous capsule. A wedge-shaped necrotic area was located at the top of an artery and a portal vein of segment 8. Necrosis was observed not only in the tumour but in the adjacent parenchyma. A histopathological examination showed that the tumour had been completely replaced by necrosis. This tumour was surrounded by capillary vessels and fed by several thick arteries, but organized thrombi were not detected. No viable cells were found. The histopathological diagnosis was a spontaneous complete necrosis of HCC caused by the occlusion of feeding vessels outside the capsule

ケイシャチ チャエン ニ オケル ジュケイ ノ カイゼン ニ カンスル ケンキュウ

茶樹の更新は,生産力を保ち,茶園管理の作業性を確保する面から樹高を低く維持するために行われるが,強いせん枝は一時的に収量が減少する。傾斜地茶園では,うねの山側と谷側部で新芽の生育が均一でないことが多く,可搬型摘採機を用いる場合,谷側部の樹高が高いと機械を高く持ち上げなければならず,困難な作業となる。そこで今回,中切りと深刈りを併用した樹形改良せん枝を行ったところ,中切りほどは摘採面幅を狭くすることなく,翌年一番茶芽の伸びが良く,茶樹の更新効果が認められた。傾斜地茶園における樹冠面の形状は,気温分布への影響を通じて一番茶収量をも左右する場合がある。改良樹形は,これまでの弧状樹形に比べ,うねの山側部と谷側部の温度差が少なく,低温の極値も高く,気象災害軽減上も有利な樹形であると考察した。また,谷側部を斜面側に角度をつけた更新方法にすることによって,摘採,せん枝,特に薬剤散布の作業性に優れた樹形となった。Causes of differences in growth of tea between the upslope sides and the downslope sides of hedges in hillside tea fields and the methods to reduce them are studied. In the arc shaped bush formation, it was found that tea grew slower on the downslope sides than on the upslope sides. The air temperature around the tea bush in winter, the daily minimum temperature, was lower on the downslope sides of hedges than on the upslope ones. The arc shaped bush formation along slopes that are pruned away deeply has less difference in the temperature of canopy surface and less difference in the growth. This method showed good effects. In addition, the operation became more efficient

Planned Marketing Adaptation and Multinationals' Choices Between Acquisitions and Greenfields

International marketing studies have extensively examined the antecedents of firms' marketing standardization/ adaptation decisions. However, it is unclear whether such decisions, once planned, codetermine the choice between buying and building foreign subsidiaries. Analyzing a sample of 150 foreign entries by Dutch firms, the authors find that the level of marketing adaptation planned for a wholly owned subsidiary is positively related to the likelihood that the subsidiary will be established through an acquisition rather than through a greenfield investment. Moreover, the authors find substantial evidence that this positive relationship is stronger for firms that (1) are establishing relatively larger subsidiaries, (2) have less experience with the industry entered, or (3) are entering less developed countries. The findings show that firms pursuing higher levels of marketing adaptation assign more value to the marketing adaptation advantages of acquisitions over greenfields, especially if the risks associated with implementing the planned adaptation level are high. In addition, firms typically strive for a fit between their international marketing strategy and their mode of foreign establishment. (authors' abstract

The Returns to Criminal Capital

Human capital theory (Becker 1962; Mincer 1958; Schultz 1960; 1961) posits that individuals can increase their labor market returns through investments in education and training. This concept has been studied extensively across several disciplines. An analog concept of criminal capital, while the focus of speculation and limited empirical study, remains considerably less developed theoretically and methodologically. This paper offers a formal theoretical model of criminal capital indicators and tests for greater illegal wage returns using a sample of serious adolescent offenders, many of whom participate in illegal income-generating activities. Our results reveal that, consistent with human capital theory, there are important illegal wage premiums associated with investments in criminal capital, notably an increasing but declining marginal return to experience and a premium for specialization. Further, as in studies of legal labor markets, we find strong evidence that, if left unaccounted for, non-random sample selection causes severe bias in models of illegal wages. Theoretical and practical implications of these results, along with directions for future research, are discussed