基于Solanum模型的云贵高原大春马铃薯潜在产量研究

[目的]计算云贵高原地区大春马铃薯潜在产量及产量差,分析产生巨大产量差的原因及解决措施。[方法]文章采用由国际马铃薯中心开发的新型植物生长模拟模型Solanum模型与田间试验相结合的方法,更精确地评估马铃薯潜在产量。[结果]云贵高原地区大春马铃薯的产量潜力巨大。云薯401潜在产量为138 t/hm~2,云薯505潜在产量为147 t/hm~2,合作88潜在产量为91.9 t/hm~2,与实际产量之间的产量差(YGM)最大的为云薯505,为117 t/hm~2,与基于FAO农业生态区域法的光温产量潜在模型算法得出的结果相符。与世界范围内已知的马铃薯潜在产量数据相比,云贵高原地区大春马铃薯的潜在产量全球最高。[结论]云贵高原地区大春马铃薯的发展潜力巨大,不同品种的潜在产量存在差异。防控晚疫病,延长生育期以充分利用太阳辐射,提高光合辐射有效利用率(RUE)是提高产量,缩小产量差的关键。     

Costs,technology and ownership of gas distribution in Italy

This paper proposes an empirical study of the Italian gas distribution industry by means of long‐term cost function. The analysis highlights the fact that the number of customers is more important than the amount of gas delivered in explaining the variability of distribution costs. Very low economies of scale, high economies of density, and the significant role of the morphologic and demographic variables characterize the nature of the technology. Better performance for private operators indicates that the privatization process should continue and the low degree of economies of scale confirms the benefits of having many operators (yardstick competition). Copyright © 2000 John Wiley & Sons, Ltd.     

Strategic online banking adoption

In this paper we study the determinants of banks’ decisions to adopt a transactional website for their customers. Using a panel of commercial banks in the United States for the period 2003–2006, we show that although bank-specific characteristics are important determinants of banks’ adoption decisions, competition also plays a prominent role. The extent of competition is related to the geographic overlap of banks in different markets and their relative market share in terms of deposits. In particular, banks adopt online banking services earlier in markets where their competitors have already adopted this technology. This paper is one of the first to construct local banking markets using the geographic market definitions delimited by the CASSIDI® Database compiled at the Federal Reserve Bank of St. Louis.     

Governance of tax courts

This paper attempts to penetrate the “black box” of the judiciary through an empirical investigation of the Italian tax courts of first instance. Both judicial delay and two-stage Data Envelopment Analysis approach with bootstrap are used to measure the efficiency of the court system and to further identify the main determinants of efficiency which, in line with the previous literature, seem to be mostly related to the judges’ effort. The study also takes advantage of an idiosyncratic feature of this branch of the Italian judiciary—in which judges are temporarily appointed and can continue to practice an external (though not conflicting) profession—to assess the impact of opportunity costs on the behavior of judges. The overall outcome confirms that judges maximize utility “the same as everybody else does” (Posner, Supreme Court Econ Rev 3:1–41, 1993).     

Anchoring Measurement of the Middle-Income Class to Subjective Evaluation

What constitutes the middle class is hotly debated. Following an income-based approach, a main issue concerns how to fix the income boundaries that define the middle-income tier. This paper offers a novel model-based approach to the use of self-reported class evaluation for identifying those boundaries. The self-declared status responses are modeled using a non-conventional parametrization of an ordered logistic model. In this parametrization, the cut-points of the model are directly interpretable as income boundaries, and the variance of the errors captures the idiosyncratic heterogeneity of the outcome variable. The use of subjective data is exemplified in the estimation of the middle class in Kazakhstan over the period 2003–2015.     

Good students,avid readers: The cost of academic success

The effects of reading habits on academic performances have been carefully investigated, but little is known about the effects of academic achievements on students’ leisure reading. This paper investigates this issue by estimating the effects of academic achievements, proxied by the number of exams passed, on leisure reading, measured by the number of leisure books read in a year. Using an online survey submitted to the students at the University of Bologna, Italy, we adopt a two-step control-function technique to control for endogeneity. The empirical evidence suggests the existence of a negative relationship between students’ academic achievements and the time devoted to leisure reading. This result holds for students of different fields of study and is stronger for male students. The Blinder–Oaxaca decomposition supports the existence of a gender-specific idiosyncratic effect.     

Having less: A personal project taxonomy of consumers' decluttering orientations,motives and emotions

This study examines consumers' orientations toward decluttering and what differentiates consumers' engagement with decluttering as a routine social practice. An internet survey was conducted with a convenience sample of 172 adult consumers who recently engaged in home decluttering projects. Cluster analysis used appraisals of personal project dimensions to create a taxonomy in which we identified three orientations toward decluttering: disengaged, enthusiastic, and challenged. Subsequent analyses compared appraisals of success and affective and motivational differences across the three orientations. Findings reveal that decluttering is enjoyable, easy, and most successful for consumers with an enthusiastic orientation who intrinsically value decluttering and link it to self-identify. Those who lack time or adequate control experience more stress and less success. Circumstances, and especially normative pressures, seemed to drive these orientations. All orientations experienced relatively high positive emotions after decluttering, which substantiates the positive influence of decluttering on emotional well-being.     

A flexible lattice framework for valuing options on assets paying discrete dividends and variable annuities embedding GMWB riders

In a market where a stochastic interest rate component characterizes asset dynamics, we propose a flexible lattice framework to evaluate and manage options on equities paying discrete dividends and variable annuities presenting some provisions, like a guaranteed minimum withdrawal benefit. The framework is flexible in that it allows to combine financial and demographic risk, to embed in the contract early exercise features, and to choose the dynamics for interest rates and traded assets. A computational problem arises when each dividend (when valuing an option) or withdrawal (when valuing a variable annuity) is paid, because the lattice lacks its recombining structure. The proposed model overcomes this problem associating with each node of the lattice a set of representative values of the underlying asset (when valuing an option) or of the personal subaccount (when valuing a variable annuity) chosen among all the possible ones realized at that node. Extensive numerical experiments confirm the model accuracy and efficiency.

     

Upstream conduct and price authority with competing organizations

We characterize the degree of price authority that competing upstream principals award their downstream agents in a setting where these agents own private information about demand and incur nonverifiable distribution costs. Principals cannot internalize these costs through monetary incentives and design “permission sets” from which agents choose prices. The objective is to understand the forces shaping delegation and the constraints imposed on equilibrium prices. When principals behave noncooperatively, agents are biased toward excessively high prices because they pass on distribution costs to consumers. Hence, the permission set only features a price cap that is more likely to bind as products become closer substitutes, in sectors where distribution is sufficiently costly, and when demand is not too volatile. By contrast, when principals behave cooperatively, the optimal delegation scheme is richer and more complex. Because principals want to charge the monopoly price, the optimal permission set features a price floor when the distribution cost is sufficiently low, it features instead full discretion for moderate values of this cost, and only when it is high enough, a price cap is optimal. Surprisingly, while competition (as captured by stronger product substitutability) hinders delegation in the noncooperative regime, the opposite occurs when principals maximize industry profit.