Trees and decisions

Summary. The traditional model of sequential decision making, for instance, in extensive form games, is a tree. Most texts define a tree as a connected directed graph without loops and a distinguished node, called the root. But an abstract graph is not a domain for decision theory. Decision theory perceives of acts as functions from states to consequences. Sequential decisions, accordingly, get conceptualized by mappings from sets of states to sets of consequences. Thus, the question arises whether a natural definition of a tree can be given, where nodes are sets of states. We show that, indeed, trees can be defined as specific collections of sets. Without loss of generality the elements of these sets can be interpreted as representing plays. Therefore, the elements can serve as states and consequences at the same time.Received: 23 January 2003, Revised: 2 November 2003, JEL Classification Numbers: C72, D70. Correspondence to: Klaus RitzbergerWe are grateful to Larry Blume, Ariel Rubinstein, Jörgen Weibull, an anonymous referee, and seminar participants at the universities of Vienna, Salamanca, and Heidelberg for helpful comments. Financial support from the Austrian Science Fund (FWF) under project P15281 is also gratefully acknowledged.     

融资融券在我国的发展研究

融资融券交易业务是与证券现货交易对应的一种证券交易业务。融资融券交易业务是证券市场上证券公司同投资者之间发生的资金或证券的借贷关系,可以分为证券市场融资交易和证券市场融券交易两方面。我国刚刚在市场上公开融资融券业务,还有很多不成熟的地方并且面临着融资融券带来的风险。对融资融券进行分析和研究,通过对比和比较的方法,选择适合我国的融资融券发展模式并提出相关对策建议,为我国的证券市场保驾护航,保障投资者的利益。     

卖空限制与收益可预测性——A股融资融券制度的证据

基于A股市场融资和融券余额的巨大差距,本文拓展了Hong et al.(2016)的理论模型,在融券端和融资端分别找到了影响股票收益率的变量:融券比率(融券余额/流通市值)和融资回补天数(融资比率/日均换手率)。进一步,本文利用组合价差法和Fama-MacBeth横截面回归法,实证检验了A股市场中融券比率与融资回补天数解释和预测股票收益率的能力。实证结果表明,在存在融券限制条件下,融券比率相比融券回补天数(融券比率/日均换手率)能更好地代表套利者对股票价格高估程度的看法,根据融券比率构建的等权重多空组合能带来月均1.58%的显著收益;而由于融资约束相对较少,融资回补天数相比融资比率(融资余额/流通市值)能更好地代表套利者对股票价格低估程度的看法,根据融资回补天数构建的等权重多空组合能带来月均1.28%的显著收益。实证结果与本文存在融券数量限制下的理论模型相符,且该收益率不能被多因子模型和常规股票特征所解释。     

异质性企业、结构转型与稳定出口

通过构建异质性企业、结构转型和出口增长的二元边际理论模型,本文认为转型国家出口增长主要沿集约边际实现的原因与其农业剩余劳动力有关,农业剩余劳动力越多,出口增长的集约边际越大、扩展边际越小。利用Tobit模型对1995-2009年中国出口到123个国家的HS-6位码贸易数据进行实证分析,在控制其他影响因素的前提下,我国农业剩余劳动力非农转移显著正向影响出口增长集约边际、负向影响扩展边际的效应确实存在。经济规模、贸易成本、人民币升值、区域经济一体化、外部冲击、语言的相通性、政治体制等变量对中国出口增长二元边际的影响机制不完全相同,表明要提高出口增长中的扩展边际比重,出口企业应实施市场多元化战略,将目标市场从传统高收入国家转移到发展中国家来,实现出口的稳定增长。     

旧城改造开发项目的容积率问题研究

随着我国城市化进程的加速推进,不断增长的城市人口与持续升级的功能需求,对现代城市的建设与发展提出了新的要求。旧城改造是提升城市形象和改善人民生活的有效手段。本文在阐述容积率相关概念的基础上,根据投入产出理论,提出了旧城改造容积率测算模型,分析了容积率与利润率之间的具体关系。旧城改造实施人员可据此提出适宜的旧城改造方案。最后,本文以重庆市某旧城改造地块为例,对其容积率进行了重新测算,提出相关规划改造方案。     

融资融券对我国期指市场影响的实证研究

以融资融券对我国期指市场的影响为对象进行实证研究,发现融资融券对期指市场当日成交金额产生负向影响,对期指市场当日持仓量产生正向作用;融资融券交易与期指市场波动性之间不存在长期稳定的协整关系,也不存在确定的线性关系;融资融券交易对期指市场当日成交金额并不存在统计意义上的因果引致关系,当日融券余额与期指市场当日持仓量存在双向因果引致关系,期指市场波动性是融券余额的单向因果引致关系。因此,扩大融资融券标的范围与可供借贷证券池,发展有利于中小投资者参与的、与融资融券交易有关的风险对冲套利金融产品是我国证券市场转型的重要举措。     

Rewilding and restoring cultural landscapes in Mediterranean mountains: Opportunities and challenges

Farmland abandonment and the decline of livestock activity in the Mediterranean mountains have resulted in dramatic landscape changes, including the generalized expansion of shrublands and forests, and the homogenization of the old cultural landscapes. This process has a variety of consequences from ecological, geomorphological and hydrological points of view, as well as from the perspectives of land management and public awareness. An intense debate currently surrounds the discussion and evaluation of rewilding (the process of passively allowing woody encroachment, as well as the reintroduction of large mammals) as an opportunity for enhancing biodiversity and restoring original landscapes after centuries of human activity versus ecological restoration (activities leading to the recovery of degraded ecosystems, including clearing and light human activity). There is no clear consensus regarding the best way to improve the ecological relationships and functioning within an ecosystem. Biodiversity and sustainability can be seen under different levels of human pressure and landscape transformation; total farmland abandonment is not always the best alternative, particularly when local inhabitants aim to sustain themselves using local resources. Many geographers and ecologists consider that extensive stockbreeding in a partially open landscape is a rational way to (i) improve landscape organization, (ii) increase flows and turnover within the ecosystems, (iii) increase the diversity of plants and animals that benefit from a relatively light human presence, and (iv) reduce wildfire risk. However, it has proven challenging for land managers and stockbreeders to clear the best old abandoned fields and “construct” a sustainable, balanced landscape that combines forests, shrublands and open lands. Private landowner involvement and support from the general public is crucial for both funding and the long-term maintenance of benefits. The best old fields should be cleared in the context of high-resolution knowledge of the topography, grassland characteristics, grassland cycles and livestock management. Such efforts are likely to be an excellent opportunity to introduce compatibility between light human activity and increases in biodiversity and sustainability for many marginal mountains, where land abandonment and general forest/shrub recovery are the inevitable tendencies. This paper examines some of the contrasting positions of the scientific community regarding the rewilding or ecological restoration of mountain landscapes, and briefly highlights some experiences in which intentional clearing of old abandoned fields has benefited stockbreeding, biodiversity, runoff generation and wildfire risks. Notably, we describe a sub-Mediterranean valley of the Iberian Range, Northern Spain, as an example. In the long term, we find that the intentional clearing of the best old fields allows the slow organization of a final landscape that will be more useful for local inhabitants, thereby helping to reverse human depopulation in these regions.     

产品内分工下制造业服务化与出口二元边际——基于系统GMM的经验研究

采用两步系统GMM估计法,在产品内分工视角下实证考察制造业服务化对出口二元边际的影响,研究发现:(1)服务化对出口市场扩展边际、产品种类扩展边际、价格边际有倒U型作用,对数量边际有抑制作用。(2)服务化对扩展边际、价格边际的倒U型作用和对数量边际的抑制作用在OECD与非OECD国家同时存在。(3)按技术复杂度划分服务部门后发现,低端服务化和高端服务化对扩展边际的影响较为一致,但低端服务化对价格边际的影响不显著,且对数量边际的抑制作用大于高端服务化。(4)产品内分工加强了服务化对价格边际的积极影响,弱化了服务化对数量边际的不利作用,但对服务化与扩展边际关系的影响不显著。深入产品内分工体系,循序渐进推动制造业服务化发展有助于提升高端出口能力,对优化出口结构有重要意义。     

The new goods margin in new markets

We analyze the role of the new goods margin in the Baltic countries’ exports and imports growth during the 1995–2008 period. Using the methodology developed in Kehoe and Ruhl (2013), we define the set of least-traded goods as those that account for the lowest 10% of total exports and imports in 1995, and then trace its growth in several markets including the Baltics’ main trade partners, the European Union and Russia. We find that, on average, by 2008 least-traded goods accounted for nearly 50% of total Baltic exports to their main trade partners. Moreover, we find that increases in the share of least-traded exports coincided with the timing of the trade liberalization reforms implemented by the Baltic countries. Least-traded imports also grew at robust rates, but their growth was lower than that of exports, accounting for slightly less than a quarter of total imports, that is, about half of the exports value. Moreover, we find that the shares of least-traded imports from the EU 15 and from Russia started diverging around the time the Baltic countries joined the EU, with the EU 15 share increasing and the Russian one declining. We also find that the Baltics’ share of least-traded exports outpaced that of other economies in Central and Eastern Europe. Finally, exports of new goods from the Baltic countries suffered noticeably during the Global Financial Crisis. After the crisis ended, the restart in new goods exports growth displayed mixed patterns.     

父母对子女的私人转移支付与子女劳动力供给

利用中国家庭金融调查(CHFS) 2013年数据,本文考察了来自父母的私人转移支付对子女劳动力供给的影响。采用父亲和母亲的受教育年限作为私人转移支付的工具变量克服了计量模型可能存在的内生性问题。研究发现,父母对子女的私人转移支付每提高1%,子女的日、周、年劳动力供给将分别降低0. 0254%、0. 0536%、0. 0991%,据此测算,父母对子女的私人转移支付每增加1元将使全国劳动力日劳动供给减少约5. 24万小时。进一步的影响机制分析发现,父母通过私人转移支付"购买"子女提供的关爱、照料服务而挤出了子女的劳动力供给是导致上述结果的重要原因。研究还发现,来自父母的私人转移支付对子女劳动力供给的影响只存在集约边际,而不存在广延边际,即其仅减少了子女的劳动供给时间,而并没有使子女退出劳动力市场。本文的研究有助于理解自上而下的代际转移支付带来的经济影响。