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Basic Hypothesis (basic + hypothesis)

Distribution by Scientific Domains

Business, Economics, Finance and Accounting	50%

Selected Abstracts

Diversity,stability relationships in multitrophic systems: an empirical exploration

JOURNAL OF ANIMAL ECOLOGY, Issue 5 2003
Priyanga Amarasekare
Summary 1The relationship between diversity and stability is crucial in understanding the dynamics of multitrophic interactions. There are two basic hypotheses about the causal link between diversity and stability. The first is that fluctuations in resource abundance allow consumer coexistence, thus increasing diversity at the consumer trophic level (resource variability hypothesis). The second is that interactions between coexisting consumer species reduce consumer efficiency and dampen population fluctuations, thus increasing consumer,resource stability (consumer efficiency hypothesis). 2The two hypotheses lead to three comparative predictions: (i) fluctuations should be greater (resource variability) or smaller (consumer efficiency) in resource populations with coexisting consumer species, compared to those invaded only by the consumer species superior at resource exploitation; (ii) average resource abundance should be greater (resource variability) or smaller (consumer efficiency) in resource populations with greater fluctuations; and (iii) removal of the consumer species inferior at resource exploitation should increase or not affect resource population fluctuations (resource variability), or always increase them (consumer efficiency). 3I tested these predictions with data from a host,multiparasitoid community: the harlequin bug (Murgantia histrionica) and two specialist parasitoids (Trissolcus murgantiae and Ooencyrtus johnsonii) that attack the bug's eggs. 4Local host populations with coexisting parasitoids exhibited smaller fluctuations and greater average abundance compared to those with just Trissolcus, the species superior at host exploitation. Local populations that lost Ooencyrtus, the species inferior at host exploitation, exhibited an increase in host population fluctuations compared to those that did not. 5The results contradict the expectations of the resource variability hypothesis, suggesting that host population fluctuations are unlikely to be driving parasitoid coexistence. They are consistent with the consumer efficiency hypothesis, that interactions between coexisting parasitoid species dampens host population fluctuations. I discuss the implications of these results as well as possible caveats. [source]

Humanitarian Crises: What Determines the Level of Emergency Assistance?

DISASTERS, Issue 2 2003
Donor Interests, Media Coverage, the Aid Business
This paper proposes a basic hypothesis that the volume of emergency assistance any humanitarian crisis attracts is determined by three main factors working either in conjunction or individually. First, it depends on the intensity of media coverage. Second, it depends on the degree of political interest, particularly related to security, that donor governments have in a particular region. Third, the volume of emergency aid depends on strength of humanitarian NGOs and international organisations present in a specific country experiencing a humanitarian emergency. The empirical analysis of a number of emergency situations is carried out based on material that has never been published before. The paper concludes that only occasionally do the media play a decisive role in influencing donors. Rather, the security interests of Western donors are important together with the presence and strength of humanitarian stakeholders, such as NGOs and international organisations lobbying donor governments. [source]

Assessment of rainfall-runoff models based upon wavelet analysis

HYDROLOGICAL PROCESSES, Issue 5 2007
Stuart N. Lane
Abstract A basic hypothesis is proposed: given that wavelet-based analysis has been used to interpret runoff time-series, it may be extended to evaluation of rainfall-runoff model results. Conventional objective functions make certain assumptions about the data series to which they are applied (e.g. uncorrelated error, homoscedasticity). The difficulty that objective functions have in distinguishing between different realizations of the same model, or different models of the same system, is that they may have contributed in part to the occurrence of model equifinality. Of particular concern is the fact that the error present in a rainfall-runoff model may be time dependent, requiring some form of time localization in both identification of error and derivation of global objective functions. We explore the use of a complex Gaussian (order 2) wavelet to describe: (1) a measured hydrograph; (2) the same hydrograph with different simulated errors introduced; and (3) model predictions of the same hydrograph based upon a modified form of TOPMODEL. The analysis of results was based upon: (a) differences in wavelet power (the wavelet power error) between the measured hydrograph and both the simulated error and modelled hydrographs; and (b) the wavelet phase. Power difference and wavelet phase were used to develop two objective functions, RMSE(power) and RMS(phase), which were shown to distinguish between simulated errors and model predictions with similar values of the commonly adopted Nash-Sutcliffe efficiency index. These objective functions suffer because they do not retain time, frequency or time-frequency localization. Consideration of wavelet power spectra and time- and frequency-integrated power spectra shows that the impacts of different types of simulated error can be seen through retention of some localization, especially in relation to when and the scale over which error was manifest. Theoretical objections to the use of wavelet analysis for this type of application are noted, especially in relation to the dependence of findings upon the wavelet chosen. However, it is argued that the benefits of localization and the qualitatively low sensitivity of wavelet power and phase to wavelet choice are sufficient to warrant further exploration of wavelet-based approaches to rainfall-runoff model evaluation. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Debt, democratization, and development in Latin America: How policy can affect global warming

JOURNAL OF POLICY ANALYSIS AND MANAGEMENT, Issue 1 2008
René W. Aubourg
The environmental Kuznets curve (EKC) hypothesis conjectures a nonlinear relationship between pollution and economic growth, such that pollution per capita initially increases as countries economically develop, but then reaches a maximum point before ultimately declining. Much of the EKC literature has focused on testing this basic hypothesis and, in studies that find evidence of an EKC, estimating the "turning point" level of development at which the per capita pollution-growth relationship changes sign. This approach has not emphasized the policy relevance of specification issues or the potential role of policy variables. This research explores a modified EKC specification which conditions the pollution-growth relationship on a country's level of debt and degree of democratization. These variables turn out to be significant, implying that different political and economic contexts can shift EKCs and their turning points. These findings suggest that policies to relieve debt burdens and institute political reform, in addition to their usual justifications, also could be used as a strategy to reduce carbon emissions from developing countries. © 2008 by the Association for Public Policy Analysis and Management. [source]

A Price Is a Signal: on Intrinsic Motivation, Crowding-out, and Crowding-in

KYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 1 2010
Friedel Bolle
SUMMARY If a previously unpaid activity (e.g. donating blood) is paid, then we often observe that this activity is reduced. In this paper, it is hypothesized that the price offered is taken as a proxy for the "value" of the activity. Depending on how the actor valued the activity previously, crowding-out or crowding-in is implied, an effect with or without persistence after stopping the payment. The model can be adapted to a number of similar situations, including those where a high price signals high costs instead of high values. Our "naïve" explanation is confronted with Bènabou and Tirole's (2003) Principal-Agent model. A questionnaire study supports our basic hypothesis as well as some of the derived consequences, and contradicts Bènabou and Tirole's model. [source]

A note on equity ownership and corporate value in Greece

MANAGERIAL AND DECISION ECONOMICS, Issue 8 2004
G.A. Karathanassis
This study attempts to investigate whether corporate performance is affected by the ownership structure, using data from companies quoted on the Athens Stock Exchange for the period 1996,1998. Given such an objective, the basic hypothesis examined, is that corporate performance as measured by Tobin's Q ratio is a function of ownership and other control variables. Our econometric approach relies on the use of a combination of time series and cross section data (panel-data analysis), a procedure that avoids many statistical problems. After examining the role of each identifiable shareholder, we find a positive relationship between institutional investors and corporate performance. Copyright © 2004 John Wiley & Sons, Ltd. [source]