Social Structure, Non-market Valuation, and Bargaining

This dissertation consists of three chapters that explore the effects of social utility on non-market values and bargaining. Chapter 1 considers the role of social networks in the valuation of public goods. In the model individuals derive utility from both their own direct enjoyment of the public good as well as from the enjoyment of those in their social network. We find that the network increases an individual\u27s valuation for the public good when members of her network have a higher weighted average valuation than she does. The network increases aggregate valuation when it assigns higher importance, that is, greater total weight, to individuals with higher private values for the public good. The model provides a theoretical foundation for the idea of opinion leaders who have disproportionate influence over their communities. The model can also guide future empirical studies by enabling a more structural approach to non-market valuation in a socially-connected group. Chapter 2 shows that yes/no responses of dichotomous choice Contingent Valuation (CV) surveys are not independent when social networks influence non-market values. The empirical CV literature has yet to attempt estimation of non-market values explicitly accommodating network effects. We investigate the statistical properties of estimates of mean willingness to pay obtained through standard approaches that ignore social networks. Monte Carlo experiments, with different types of simulated and real world social networks, indicate that failure to account for network effects leads to underestimation of non-market values. Chapter 3 reports results of an experiment designed to explore the trade-offs between added surplus and lost bargaining power in long-term contracting. Participants played a sequential bargaining game whereby the first mover (the procurer) selects whether to be the recipient in a single-shot dictator game or a twice-repeated ultimatum game. We find that, in general, participants prefer to retain the bargaining power of the ultimatum games as opposed to engage in a dictator game played over a bigger endowment. This result suggests that diminished bargaining power can be a serious detriment to realizing long-term gains from trade

Food security in developing countries: Gender and spatial interactions

This brief summarizes findings of a project entitled “Food Security in Developing Countries: Gender and Spatial Interactions’” undertaken by researchers from the University of Alberta. The project uses a large cross-sectional dataset from the Integrated Modelling Platform for Mixed Animal Crop systems (IMPACT) Lite collected by Climate Change, Agriculture, and Food Security (CCAFS) from 2010 to late 2012. This dataset surveyed 1,500 households located across seven countries in Africa and Asia. The project focused on estimating three spatial effects on food security: i) a spatial autoregressive effect that measures how neighbors’ food security influences a farmer’s food security; ii) how these spatial effects differ for male and female-headed households; and iii) how the food security of neighbors of the same gender affect their own food security

Characterizing social networks and their effects on income diversification in rural Kerala, India

Social context is an important determinant of income diversification. In India, caste and ethnicity provide the basis for multi-functional social networks. This paper considers the effects of intra-village social networks on household income diversification in one of the poorest and most ethnically diverse areas of Kerala, India. Using techniques adapted from spatial econometrics, findings show that average diversification of a household’s social network has a positive effect on its income diversification by a factor of 3.6. Results of the study suggest that social stratification in villages with higher levels of stratification are associated with lower levels of income diversification

The Spitzer c2d Survey of Weak-line T Tauri Stars II: New Constraints on the Timescale for Planet Building

One of the central goals of the Spitzer Legacy Project ``From Molecular Cores to Planet-forming Disks'' (c2d) is to determine the frequency of remnant circumstellar disks around weak-line T Tauri stars (wTTs) and to study the properties and evolutionary status of these disks. Here we present a census of disks for a sample of over 230 spectroscopically identified wTTs located in the c2d IRAC (3.6, 4.5, 4.8, and 8.0 um) and MIPS (24 um) maps of the Ophiuchus, Lupus, and Perseus Molecular Clouds. We find that ~20% of the wTTs in a magnitude limited subsample have noticeable IR-excesses at IRAC wavelengths indicating the presence of a circumstellar disk. The disk frequencies we find in these 3 regions are ~3-6 times larger than that recently found for a sample of 83 relatively isolated wTTs located, for the most part, outside the highest extinction regions covered by the c2d IRAC and MIPS maps. The disk fractions we find are more consistent with those obtained in recent Spitzer studies of wTTs in young clusters such as IC 348 and Tr 37. From their location in the H-R diagram, we find that, in our sample, the wTTs with excesses are among the younger part of the age distribution. Still, up to ~50% of the apparently youngest stars in the sample show no evidence of IR excess, suggesting that the circumstellar disks of a sizable fraction of pre-main-sequence stars dissipate in a timescale of ~1 Myr. We also find that none of the stars in our sample apparently older than ~10 Myrs have detectable circumstellar disks at wavelengths < 24 um. Also, we find that the wTTs disks in our sample exhibit a wide range of properties (SED morphology, inner radius, L_DISK/L*, etc) which bridge the gaps observed between the cTTs and the debris disk regimes.Comment: 54 pages, 13 figures, Accepted by Ap

An MDA approach for developing Secure OLAP applications: metamodels and transformations

Decision makers query enterprise information stored in Data Warehouses (DW) by using tools (such as On-Line Analytical Processing (OLAP) tools) which employ specific views or cubes from the corporate DW or Data Marts, based on multidimensional modelling. Since the information managed is critical, security constraints have to be correctly established in order to avoid unauthorized access. In previous work we defined a Model-Driven based approach for developing a secure DW repository by following a relational approach. Nevertheless, it is also important to define security constraints in the metadata layer that connects the DW repository with the OLAP tools; that is, over the same multidimensional structures that end users manage. This paper incorporates a proposal for developing secure OLAP applications within our previous approach: it improves a UML profile for conceptual modelling; it defines a logical metamodel for OLAP applications; and it defines and implements transformations from conceptual to logical models, as well as from logical models to secure implementation in a specific OLAP tool (SQL Server Analysis Services).This research is part of the following projects: SIGMA-CC (TIN2012-36904), GEODAS-BC (TIN2012-37493-C01) and GEODAS-BI (TIN2012-37493-C03) funded by the Ministerio de Economía y Competitividad and Fondo Europeo de Desarrollo Regional FEDER. SERENIDAD (PEII11-037-7035) and MOTERO (PEII11- 0399-9449) funded by the Consejería de Educación, Ciencia y Cultura de la Junta de Comunidades de Castilla La Mancha, and Fondo Europeo de Desarrollo Regional FEDER

The Spitzer c2d Survey of Weak-Line T Tauri Stars. III. The Transition from Primordial Disks to Debris Disks

We present 3.6 to 70 {\mu}m Spitzer photometry of 154 weak-line T Tauri stars (WTTS) in the Chamaeleon, Lupus, Ophiuchus and Taurus star formation regions, all of which are within 200 pc of the Sun. For a comparative study, we also include 33 classical T Tauri stars (CTTS) which are located in the same star forming regions. Spitzer sensitivities allow us to robustly detect the photosphere in the IRAC bands (3.6 to 8 {\mu}m) and the 24 {\mu}m MIPS band. In the 70 {\mu}m MIPS band, we are able to detect dust emission brighter than roughly 40 times the photosphere. These observations represent the most sensitive WTTS survey in the mid to far infrared to date, and reveal the frequency of outer disks (r = 3-50 AU) around WTTS. The 70 {\mu}m photometry for half the c2d WTTS sample (the on-cloud objects), which were not included in the earlier papers in this series, Padgett et al. (2006) and Cieza et al. (2007), are presented here for the first time. We find a disk frequency of 19% for on-cloud WTTS, but just 5% for off- cloud WTTS, similar to the value reported in the earlier works. WTTS exhibit spectral energy distributions (SEDs) that are quite diverse, spanning the range from optically thick to optically thin disks. Most disks become more tenuous than Ldisk/L* = 2 x 10^-3 in 2 Myr, and more tenuous than Ldisk/L* = 5 x 10^-4 in 4 Myr.Comment: 40 pages, 13 figures, 4 tables. Accepted for publication in ApJ on September 20, 201

Social Networks and Non-market Valuations *

Abstract This paper considers the role of social networks in the non-market valuation of public goods. In the model individuals derive utility from both their own direct enjoyment of the public good as well as from the enjoyment of those in their network. We find that network structure almost always matters, both for utility and for valuation. The network increases aggregate valuation when it assigns higher importance, that is, greater total weight, to individuals with higher private values for the public good. The model provides a theoretical foundation for the idea of opinion leaders who have disproportionate influence over their communities. Specifically, opinion leaders are individuals assigned high importance by the network, and projects favored by opinion leaders tend to be favored by the network as a whole. The model can also guide future empirical studies by enabling a more structural approach to non-market valuation in a socially-connected group

The duration compression effect is mediated by adaptation of both retinotopic and spatiotopic mechanisms

The duration compression effect is a phenomenon in which prior adaptation to a spatially circumscribed dynamic stimulus results in the duration of subsequent subsecond stimuli presented in the adapted region being underestimated. There is disagreement over the frame of reference within which the duration compression phenomenon occurs. One view holds that the effect is driven by retinotopic-tuned mechanisms located at early stages of visual processing, and an alternate position is that the mechanisms are spatiotopic and occur at later stages of visual processing (MT+). We addressed the retinotopic-spatiotopic question by using adapting stimuli – drifting plaids - that are known to activate global-motion mechanisms in area MT. If spatiotopic mechanisms contribute to the duration compression effect, drifting plaid adaptors should be well suited to revealing them. Following adaptation participants were tasked with estimating the duration of a 600ms random dot stimulus, whose direction was identical to the pattern direction of the adapting plaid, presented at either the same retinotopic or the same spatiotopic location as the adaptor. Our results reveal significant duration compression in both conditions, pointing to the involvement of both retinotopic-tuned and spatiotopic-tuned mechanisms in the duration compression effect