Ein Rollstuhl muss passen wie ein Schuh

Zusammenfassung  Eine Rollstuhlanpassung in fünf Akten — K?nnen Sie sich Ihren Arbeitsalltag ohne den Rollstuhl vorstellen? Sicher nicht. Doch allzu oft kommt der n?chstbeste Stuhl zum Einsatz – ungeachtet der K?rperma?e der Person, die ihn benutzen soll und die dann eher schlecht als recht darin sitzt. Doch schon kleinste Ver?nderungen an Rücklehne oder Sitzposition k?nnen Ihrem Patienten helfen. Oliver Kopplin gibt Pflegekr?ften Tipps, worauf sie bei Patienten im Rollstuhl achten sollten.     

STOCK RETURNS AND VOLATILITY ON CHINA'S STOCK MARKETS

We examine time‐series features of stock returns and volatility, as well as the relation between return and volatility in four of China's stock exchanges. Variance ratio tests reject the hypothesis that stock returns follow a random walk. We find evidence of long memory of returns. Application of GARCH and EGARCH models provides strong evidence of time‐varying volatility and shows volatility is highly persistent and predictable. The results of GARCH‐M do not show any relation between expected returns and expected risk. Daily trading volume used as a proxy for information arrival time has no significant explanatory power for the conditional volatility of daily returns. JEL classification: G15     

Naive learning and cooperation in network experiments

In this paper we study learning and cooperation in repeated prisoners' dilemmas experiments. We compare interaction neighbourhoods of different size and structure, we observe choices under different information conditions, and we estimate parameters of a learning model.We find that naive imitation, although a driving force in many models of spatial evolution, may be negligible in the experiment. Naive imitation predicts more cooperation in spatial structures than in spaceless ones—regardless whether interaction neighbourhoods have the same or different sizes in both structures. We find that with some interaction neighbourhoods even the opposite may hold.     

Cybersecurity: Stakeholder incentives,externalities, and policy options

Information security breaches are increasingly motivated by fraudulent and criminal motives. Reducing their considerable costs has become a pressing issue. Although cybersecurity has strong public good characteristics, most information security decisions are made by individual stakeholders. Due to the interconnectedness of cyberspace, these decentralized decisions are afflicted with externalities that can result in sub-optimal security levels. Devising effective solutions to this problem is complicated by the global nature of cyberspace, the interdependence of stakeholders, as well as the diversity and heterogeneity of players. The paper develops a framework for studying the co-evolution of the markets for cybercrime and cybersecurity. It examines the incentives of stakeholders to provide for security and their implications for the ICT ecosystem. The findings show that market and non-market relations in the information infrastructure generate many security-enhancing incentives. However, pervasive externalities remain that can only be corrected by voluntary or government-led collective measures.     

Temporary immigration visas

This paper deals with recent proposals concerning temporary immigration visas as a means to combat the problem of illegal immigration. We set up a simple two-period model of international migration between a poor South and a rich North with temporary visas issued for one period. Because of capital market imperfections, immigrants from the South face additional capital costs when financing the visa fee. In this model, we find that temporary visas can improve welfare in the North if capital costs of the immigrants are sufficiently low. For high capital costs, however, a welfare reduction cannot be ruled out. We extend the model to the case of heterogeneous immigrants and asymmetric information. In this setting, we show that the government in the North may have an incentive to issue temporary visas for those with low capital costs and to tolerate illegal immigration of the others.     

The costs of increased localization for a multiple-product food supply chain: Dairy in the United States

There is increased interest in greater localization of food supply chains but little evidence about the effects of localization on supply-chain costs. Assessing these effects is complex in multiple-product, multi-process supply chains such as the dairy industry. In this study, we develop a spatially-disaggregated transshipment model for the US dairy sector that minimizes total supply-chain costs, including assembly, processing, interplant transportation and final product distribution. We employ the cost-minimizing solution as benchmark to compare alternative scenarios of increased supply chain localization. Our results indicate: (1) short-run limits to increased localization, (2) modest impacts on overall supply-chain costs, and (3) large cost re-allocations across supply chain segments, regions and products. We find that increased localization reduces assembly costs while increase processing and distribution costs. Cost increases are larger in regions with smaller raw milk supplies and during the season when less raw milk is produced. Minimizing distances traveled by all dairy products results in tradeoffs across products in terms of cost and distance traveled. The relationship between increased localization and costs appears to be nonlinear.