关于上海城市“地标性”植物群落建设的思考

以上海中心城区绿地为研究对象,从植物群落角度,对不同绿地类型进行植物社会学调查,并对群落的自然度进行评价,剖析当前城市绿地建设中存在的问题。针对群落自然度低、地带性特色不足、未遵循区域自然演替规律的问题,提出"地标性"植物群落的概念与构建方法。     

Atheoretical macroeconometrics: A critique

The spurious nature of the restrictions used to identify many macroeconometric models has led some researchers to advocate a style of econometric inquiry that is less dependent on prior theoretical restrictions of the sort that were central to the approach of the Cowles Commission. This development, which we call atheoretical macroeconometrics, is summarized and evaluated in the current paper. It is contrasted with an updated version of the Cowles Commission approach. We conclude that while some of the exercises of atheoretical macroeconometrics are valid, those that have attracted the most attention and appear the most innovative-exogeneity testing, impulse response analysis and policy analysis using estimated vector autoregressions - are based on incorrect analysis.     

What Moves Investment Growth?

We use accounting identities to decompose unexpected changes in investment growth into surprises to current cash‐flow growth and stock returns, and revisions of expectations about future cash‐flow growth and future discount rates. Using a vector autoregressive model we find that current cash‐flow surprises account for the largest element of the variance decomposition. Investment growth and current cash‐flow surprises are negatively correlated with news about future cash‐flow growth, which can be expected from persistent productivity shocks and decreasing returns to scale. We find little evidence of a discount rate channel for investment since return terms are small and have unintuitive signs.     

Contrasting roles of financial theory and practice

Reconcilation between conflicting roles of financial theory and practice reveals a common ground. A framework is presented for placing financial theory and practice in perspective.     

政府产品创新补贴下的企业R＆D策略选择

为了研究在政府产品创新补贴政策下企业的R＆D策略选择问题,建立了双寡头市场中面向工艺R＆D的三阶段博弈模型：第一阶段政府以社会福利最大为目标选择产品创新补贴率;第二阶段企业进行R＆D投资以降低生产成本;第三阶段企业在产品市场中进行古诺竞争。根据双寡头在第二和第三阶段是否合作,给出了研发竞争、研发卡特尔、技术共享联盟和研究共同体等四种R＆D策略,得到了相应的政府最优R＆D补贴率。研究表明：从企业的R＆D投入和产品产量的角度看,当溢出效应较高时,研发竞争策略优于研发卡特尔策略;当溢出效应较低时,研发卡特尔策略优于研发竞争策略。研发卡特尔策略与研发竞争策略相比,研发卡特尔更能推动企业利润的提高并且可以改善社会总福利。从产品产量、企业利润和社会总福利最大化角度考虑,研究共同体为四种策略中的最优策略。