Will It Spread or Not? The Effects of Social Influences and Network Topology on Innovation Diffusion

Innovation diffusion theory suggests that consumers differ concerning the number of contacts they have and the degree and the direction to which social influences determine their choice to adopt. To test the impacts of these factors on innovation diffusion, in particular the occurrence of hits and flops, a new agent‐based model for innovation diffusion is introduced. This model departs from existing percolation models by using more realistic agents (both individual preferences and social influence) and more realistic networks (scale free with cost constraints). Furthermore, it allows consumers to weight the links they have, and it allows links to be directional. In this way this agent‐based model tests the effect of VIPs who can have a relatively large impact on many consumers. Results indicate that markets with high social influence are more uncertain concerning the final success of the innovation and that it is more difficult for the innovation to take off. As consumers affect each other to adopt or not at the beginning of the diffusion, the new product has more difficulties to reach the critical mass that is necessary for the product to take off. In addition, results of the simulation experiments show under which conditions highly connected agents (VIPs) determine the final diffusion of the innovation. Although hubs are present in almost any network of consumers, their roles and their effects in different markets can be very different. Using a scale‐free network with a cut‐off parameter for the maximum number of connections a hub can have, the simulation results show that when hubs have limits to the maximum number of connections the innovation diffusion is severely hampered, and it becomes much more uncertain. However, it is found that the effect of VIPs on the diffusion curve is often overestimated. In fact when the influence of VIPs on the decision making of the consumers is strengthened compared with the influence of normal friends, the diffusion of the innovation is not substantially facilitated. It can be concluded that the importance of VIPs resides in their capacity to inform many consumers and not in a stronger persuasive power.     

Public information arrival and volatility persistence in financial markets

This paper explores the relationship between daily market volatility and the arrival of public information in four different financial markets. Public information is measured as the daily number of economic news headlines, divided in six categories of news. Statistical analysis of the news data suggests the presence of particular seasonality effects, as well as a strong degree of autocorrelation. Over the period 1994–1998, significant effects of specific news categories on the volatility of US stocks, treasury bills, bonds and dollar were detected. However, the effects – in size and duration – vary by news category and by financial market. It is demonstrated that most of the volatility persistence, as observed by GARCH models, tends to disappear when news is included in the conditional variance equation.     

Local asymptotic normality for randomly censored models with applications to rank tests

For randomly right censored models we study the asymptotic behaviour of linear (rank) statistics under local alternatives. The results can be used to evaluate the asymptotic power of the corresponding tests. For instance we treat the question how to choose the best scores in order to derive asymptotically optimal (rank) tests under certain alternatives.     

Diversity of incentives for private forest landowners: An assessment of programs in Indiana, USA

 Many government and private programs provide incentives for non-industrial private forest (NIPF) owners. Due to the complexity of this web of programs, the incentives of the programs are unclear. We focus on four specific programs that represent different rule structures—a federal cost-share program, a state tax incentive program, a nationwide private stewardship program, and a local private conservation organization. We perform institutional analysis of the formal and informal rules of the programs based on literature review, discussions with officers, and formal guidelines of the programs. We classify different types of rule structures, and explain them in relation to goals and organizational structures of the programs.     

On durable goods markets with entry and adverse selection

Abstract. We investigate the nature of trading and sorting induced by the dynamic price mechanism in a competitive durable good market with adverse selection and exogenous entry of traders over time. The model is a dynamic version of Akerlof (1970) . Identical cohorts of durable goods, whose quality is known only to potential sellers, enter the market over time. We show that there exists a cyclical equilibrium where all goods are traded within a finite number of periods after entry. Market failure is reflected in the length of waiting time before trade. The model also provides an explanation of market fluctuations. JEL classification: D82 A propos des marchés de biens durables quand il y a entrée de nouveaux commerçants et sélection adverse. Les auteurs analysent la nature du commerce et du triage engendrés par le mécanisme dynamique des prix dans un marché concurrentiel de biens durables quand il y a sélection adverse et entrée exogène de nouveaux commerçants dans le temps. Ce modèle est une version dynamique du modèle d’ Akerlof (1970) . Des cohortes identiques de biens durables, dont la qualité est connue seulement des vendeurs potentiels, arrivent sur le marché dans le temps. Il semble qu’il y ait plus de commerce actif que ce qui est prévu par un modèle statique. En particulier, on montre qu’il existe un équilibre cyclique où tous les biens sont transigés à l’intérieur d’un nombre fini de périodes après leur arrivage et que, à chaque phase du cycle, l’éventail de qualité des biens transigés s’accroît. Les commerçants qui transigent des produits de plus haute qualité attendent plus longtemps et l’imperfection du marché se traduit par la longueur de temps d’attente avant la transaction. Le modèle fournit aussi une explication des fluctuations du marché.     

A landscape approach for assessing the biodiversity value of indigenous forest remnants: Case study of the Manawatu/Wanganui region of New Zealand

To halt the decline of biodiversity in New Zealand, the government has formulated a strategy of maintaining and restoring a full range of remaining natural habitats to a healthy functioning state. Many indigenous forest remnants exist on private land, and these could be utilised to increase biodiversity. Resources for conservation of forest remnants are limited, so they must be used wisely to deliver the greatest possible biodiversity gain. This paper presents a rapid method for valuing the biodiversity of a region's indigenous forest remnants to help prioritise conservation resources. The region is divided into environmentally distinct areas called land environments. A detailed land-cover map is derived from satellite imagery and used to estimate the proportion of natural habitats remaining in each land environment; from this the biodiversity value of any forest remnant may be calculated. The method is rapid and does not require detailed biodiversity information. When combined with conservation costs, it may be used to create a priority list of forest remnants for conservation. The Manawatu/Wanganui region of New Zealand is used as a case study to demonstrate the method.     

May business mentors act as opportunity brokers and enablers among university students?

Networks are recognized as a central component of the entrepreneurial process, in particular with regard to opportunity identification and exploitation. In this study, we specifically analyze the role of mentors who are in business as opportunity brokers and enablers among university students with entrepreneurial intentions. Our investigation on 1022 students from 13 French-language universities based in Canada, France, Belgium and Algeria indicates that mentors in business, contrary to other mentors, support opportunity identification and exploitation among university students. Although student gender, entrepreneurial experience and education have a more pronounced effect, mentoring is the only element that can be controlled for through the creation of formal support programs. These results call on public authorities, and universities in particular, to implement formal mentoring programs to support students who are interested in starting their own business, and who would not otherwise have access to business mentors in their environment.