The Price of Local Fairness in Multistage Selection

International audienc

Multistage Game Models and Delay Supergames

Prize Lecture to the memory of Alfred Nobel, December 9, 1994.Game Theory;

On Fair Selection in the Presence of Implicit Variance

Quota-based fairness mechanisms like the so-called Rooney rule or four-fifths rule are used in selection problems such as hiring or college admission to reduce inequalities based on sensitive demographic attributes. These mechanisms are often viewed as introducing a trade-off between selection fairness and utility. In recent work, however, Kleinberg and Raghavan showed that, in the presence of implicit bias in estimating candidates' quality, the Rooney rule can increase the utility of the selection process. We argue that even in the absence of implicit bias, the estimates of candidates' quality from different groups may differ in another fundamental way, namely, in their variance. We term this phenomenon implicit variance and we ask: can fairness mechanisms be beneficial to the utility of a selection process in the presence of implicit variance (even in the absence of implicit bias)? To answer this question, we propose a simple model in which candidates have a true latent quality that is drawn from a group-independent normal distribution. To make the selection, a decision maker receives an unbiased estimate of the quality of each candidate, with normal noise, but whose variance depends on the candidate's group. We then compare the utility obtained by imposing a fairness mechanism that we term $\gamma$-rule (it includes demographic parity and the four-fifths rule as special cases), to that of a group-oblivious selection algorithm that picks the candidates with the highest estimated quality independently of their group. Our main result shows that the demographic parity mechanism always increases the selection utility, while any $\gamma$-rule weakly increases it. We extend our model to a two-stage selection process where the true quality is observed at the second stage. We discuss multiple extensions of our results, in particular to different distributions of the true latent quality.Comment: 27 pages, 10 figures, Economics and Computation (EC'20

Low-Income Consumers in Brazil: Nuances of a Market That Can No Longer Be Ignored

The main goal of this paper is to better understand the low income Brazilian market, supported by two basic concepts: price unfairness and perceived product value. In order to meet the research objective a qualitative approach, based on two methodological procedures – observation and in-depth interviews –, was used. The findings indicate that small neighborhood retailers, despite lacking adequate physical infrastructure and management skills, play an important role in meeting the needs of low-income consumers. They offer convenience, personalized services, easy and uncomplicated credit (on an informal basis), and a product mix that matches the needs and desires of their customers. It was also found that although these small retailers charge higher prices than large supermarket chains, their customers still see value in their offerings and do not consider the prices asked to be unfair: they recognize that the benefits they receive outweigh the higher prices they pay. It was also found that low-income consumers relate with neighborhood retail stores in a basis that goes beyond the mere business, but in a cultural basis too. These small stores function not only as points of sale, but also as places where people can meet and discuss issues related to the local community. The principal contribution of this paper is in providing substantive information about the nuances of a market that has hitherto not been adequately explored but that holds a potential that can no longer be ignored. In Brazil, this market contains nearly 90 million consumers, eager to be included in the world of consumption. The findings presented by this study are of relevance not only to academic organisations and businesses, but also to social organizations and public policymakers responsible for improving the quality of life of the poor

Lab and life: Does risky choice behaviour observed in experiments reflect that in the real world?

Risk preferences play a crucial role in a great variety of economic decisions. Measuring risk preferences reliably is therefore an important challenge. In this paper we ask the question whether risk preferences observed in economic experiments reflect real-life risky choice behaviour. We investigate in a sample representative for a rural region of eastern Uganda whether pursuing farming strategies with both a higher expected profit and greater variance of profits is associated with willingness to take risks in an experiment. Controlling for other determinants of risk-taking in agriculture, we find that risky choice behaviour in the experiment is correlated with risky choice behaviour in real life in one domain, i.e. the purchase of fertiliser, but not in other domains, i.e. the growing of cash crops and market-orientation more broadly. Our findings suggest that economic experiments may be good at capturing real-world risky choice behaviour that is narrowly bracketed

Can a novel management plan for the Bering Sea and Aleutian Islands crab fisheries succeed?

Since their inception, Bering Sea/Aleutian Islands (BSAI) crab fisheries have attracted participants willing to undertake great financial and personal risks to participate in these high valued fisheries. Although entry to the fisheries is limited, excess capital and overcapacity, together with stock declines, have resulted in a race for fish. The shortest season is in the Bristol Bay red king crab fishery, which has been prosecuted for less than one week in recent years. Efforts of managers to protect declining stocks by reducing allowable catch have increased the economic stress on participants and communities that depend on these fisheries and increased pressure on participants to take greater risks. For several years, the North Pacific Fishery Management Council worked with participants to address these problems in the crab fisheries through series of working groups and management measures. In 2001, Congress stepped in, directing the Council to assess various rationalization programs for the fisheries, including individual fishing quotas (IFQs), processor shares, cooperatives, and quotas held by communities. The outcome of the Council process is a new and unique management program selected by a unanimous vote of the North Pacific Council. The program reflects the Council's desire to accommodate the interests of several groups dependent on these fisheries-vessel owners, processors, captains and crew, and communities. Under the program, harvest quota shares (QS) will be issued to vessel owners and captains. Processors will be issued processing quota shares. Under these allocations, 90 percent of harvest quota shares are designated for delivery to holders of processing quota shares. Community interests are protected by a requirement that a certain portion of the catch be landed and processed in designated regions. An arbitration program is included to resolve price disputes, which could arise because of the constraints on markets created by the dual share allocations. The result of the Council's action is one of the most complex fishery management programs to date. The attempt to satisfy many interests creates significant hurdles that must be overcome for the program to succeed economically and environmentally. This paper describes key dimensions of the proposed crab fishery management program and identifies the most substantial hurdles that the program must overcome for the Council to judge it a successful management program for the fisheries. First, managers will be challenged by program implementation. Implementation will require initial allocations of harvesting shares to vessel owners and captains and processing shares to processors. Most shares will be regionally designated based on the participant's landings history. Second, managers will face the challenge of protecting stocks as the incentives to high grade increase in the share-based fishery. Third, the markets for the harvest shares, captains shares, and processing shares must develop in a manner that facilitates coordination of harvesting and processing activity required by the share system and the regional landing and processing requirements. Lastly, market opportunities for harvest landings will be constrained by the requirement that deliveries be made to a processing share holder in a designated region. For the program to be considered a success, price formation in the market for landings must be perceived as fair. Each of these issues is described in a manner that provides the reader with a perspective of the institutional challenges faced by a program that attempts to address the concerns of several different interests. In addition, characteristics of the fisheries that contribute to the potential to overcome these obstacles are discussed.Resource /Energy Economics and Policy,

Predictors of Turnover Intention Among Employees in Nigeria’s Oil Industry

It has been debated in literature whether context more than disposition predicts organizational outcomes, but the extent to which they predict employee turnover intention has been evaded, whereas beyond theorising, this may have important consequences for employee retention and performance strategy. The predictive roles of contextual (distributive, procedural and interactional justice) and dispositional variables (conscientiousness, agreeableness and emotional stability) on turnover intention among employees in Nigeria’s oil industry were examined. Using cross-sectional survey design and multistage sampling techniques (n =750) employees comprising 534 (71.2%) males and 216 (28.8%) females with a mean age of 35 years and standard deviation of 6.88 participated in the study. The sampling frame in all 12 out of 32 companies from four clusters that make up Nigeria’s oil industry was formed using quota, proportionate and simple random sampling techniques. Data was collected using validated measures of the study variables combined into a single survey questionnaire. Significant negative relationship was found between contextual variables and turnover intention, and between dispositional variables and turnover intention respectively. Controlling for age and tenure, contextual variables accounted for higher variance in turnover intention (R2 = 0.098; F (5, 745) = 22.23, p < .001) ) than dispositional variables (R2 = 0.10; F (8, 742) = 1.51. p < .001, justifying the assumption of weak effects of dispositional traits in strong situations. Managerial implications of the findings are discussed

High-Capacity Clos-Network Switch for Data Center Networks

Scaling-up Data Center Networks (DCNs) should be done at the network level as well as the switching elements level. The glaring reason for this, is that switches/routers deployed in the DCN can bound the network capacity and affect its performance if improperly chosen. Many multistage switching architectures have been proposed to fit for the next-generation networking needs. However all of them are either performance limited or too complex to be implemented. Targeting scalability and performance, we propose the design of a large-capacity switch in which we affiliate a multistage design with a Networks-on- Chip (NoC) design. The proposal falls into the category of buffered multistage switches. Still, it has a different architectural aspect and scheduling process. Dissimilar to common point-to-point crossbars, NoCs used at the heart of the three-stage Clos-network allow multiple packets simultaneously in the modules where they can be adaptively transported using a pipelined scheduling scheme. Our simulations show that the switch scales well with the load and size variation. It outperforms a variety of architectures under a range of traffic arrivals

Land Tenure, Governance and Accountability in Nigeria: The Implications on Food Production to Feed the Present and the Future

Land is very vital for agricultural production, and for any nation that wants to be self-food sufficient. Different land reforms have taken place in Nigeria since 1960 with the aim of facilitating access to agricultural land, and make the nation self-sufficient in food production, but little changes have only been recorded. Bureaucracy by approving authorities in practice in communities where land is situated still hinders land acquisition for agricultural investment. This study therefore analyzes land policy, governance and accountability and draw out some implications on food production in Nigeria. The percentage of arable land to the total land area was 37.3 percent by available data in 2013, which suggests that smaller area is only available for cultivation with little for agricultural expansion. There may likely be a great challenge in producing enough food to sustain the future population of Nigeria if issues on land tenure and governance are not addressed. Even though our finding revealed that Nigerians cultivate more land at present than ever before with a percentage increase of 19.2 percent in 2000 to 2010, much needs to be done considering challenges confronting agricultural investors. Some of the identified challenges in Ogun State include: the activities of nomadic, high cost of land acquisition, land grabbing which has dispossessed members of the communities of their large parcels of land, scarcity of labor in rural community due to youth rural-urban drift and high cost of modern agricultural input preventing them to adopt. This is a dangerous trend for the future considering the current food deficit problem in Nigeria. Transparency in land governance with customary laws can improve land access. Removal of gender biases in access to land, bureaucracy and cost of securing and perfecting title, short-term lease which cannot be used as collateral for agricultural loans in the Land Use Act need to be amended

Energy Saving and Virtualization Technologies in Switching

Switching is the key functionality for many devices like electronic Router and Switch, optical Router, Network on Chips (NoCs) and so on. Basically, switching is responsible for moving data unit from one port/location to another (or multiple) port(s)/location(s). In past years, the high capacity, low delay were the main concerns when designing high-end switching unit. As new demands, requests and technologies emerge, flexibility and low power cost switching design become to weight the same as throughput and delay. On one hand, highly flexible (i.e, programming ability) switching can cope with variable needs stem from new applications (i.e, VoIP) and popular user behavior (i.e, p2p downloading); on the other hand, reduce the energy and power dissipation for switching could not only save bills and build echo system but also expand components life time. Many research efforts have been devoted to increase switching flexibility and reduce its power cost. In this thesis work, we consider to exploit virtualization as the main technique to build flexible software router in the first part, then in the second part we draw our attention on energy saving in NoC (i.e, a switching fabric designed to handle the on chip data transmission) and software router. In the first part of the thesis, we consider the virtualization inside Software Routers (SRs). SR, i.e, routers running in commodity Personal Computers (PCs), become an appealing solution compared to traditional Proprietary Routing Devices (PRD) for various reasons such as cost (the multi-vendor hardware used by SRs can be cheap, while the equipment needed by PRDs is more expensive and their training cost is higher), openness (SRs can make use of a large number of open source networking applications, while PRDs are more closed) and flexibility. The forwarding performance provided by SRs has been an obstacle to their deployment in real networks. For this reason, we proposed to aggregate multiple routing units that form an powerful SR known as the Multistage Software Router (MSR) to overcome the performance limitation for a single SR. Our results show that the throughput can increase almost linearly as the number of the internal routing devices. But some other features related to flexibility (such as power saving, programmability, router migration or easy management) have been investigated less than performance previously. We noticed that virtualization techniques become reality thanks to the quick development of the PC architectures, which are now able to easily support several logical PCs running in parallel on the same hardware. Virtualization could provide many flexible features like hardware and software decoupling, encapsulation of virtual machine state, failure recovery and security, to name a few. Virtualization permits to build multiple SRs inside one physical host and a multistage architecture exploiting only logical devices. By doing so, physical resources can be used in a more efficient way, energy savings features (switching on and off device when needed) can be introduced and logical resources could be rented on-demand instead of being owned. Since virtualization techniques are still difficult to deploy, several challenges need to be faced when trying to integrate them into routers. The main aim of the first part in this thesis is to find out the feasibility of the virtualization approach, to build and test virtualized SR (VSR), to implement the MSR exploiting logical, i.e. virtualized, resources, to analyze virtualized routing performance and to propose improvement techniques to VSR and virtual MSR (VMSR). More specifically, we considered different virtualization solutions like VMware, XEN, KVM to build VSR and VMSR, being VMware a closed source solution but with higher performance and XEN/KVM open source solutions. Firstly we built and tested each single component of our multistage architecture (i.e, back-end router, load balancer )inside the virtual infrastructure, then and we extended the performance experiments with more complex scenarios like multiple Back-end Router (BR) or Load Balancer (LB) which cooperate to route packets. Our results show that virtualization could introduce 40~\% performance penalty compare with the hardware only solution. Keep the performance limitation in mind, we developed the whole VMSR and we obtained low throughput with 64B packet flow as expected. To increase the VMSR throughput, two directions could be considered, the first one is to improve the single component ( i.e, VSR) performance and the other is to work from the topology (i.e, best allocation of the VMs into the hardware ) point of view. For the first method, we considered to tune the VSR inside the KVM and we studied closely such as Linux driver, scheduler, interconnect methodology which could impact the performance significantly with proper configuration; then we proposed two ways for the VMs allocation into physical servers to enhance the VMSR performance. Our results show that with good tuning and allocation of VMs, we could minimize the virtualization penalty and get reasonable throughput for running SRs inside virtual infrastructure and add flexibility functionalities into SRs easily. In the second part of the thesis, we consider the energy efficient switching design problem and we focus on two main architecture, the NoC and MSR. As many research works suggest, the energy cost in the Communication Technologies ( ICT ) is constantly increasing. Among the main ICT sectors, a large portion of the energy consumption is contributed by the telecommunication infrastructure and their devices, i.e, router, switch, cell phone, ip TV settle box, storage home gateway etc. More in detail, the linecards, links, System on Chip (SoC) including the transmitter/receiver on these variate devices are the main power consuming units. We firstly present the work on the power reduction of the data transmission in SoC, which is carried out by the NoC. NoC is an approach to design the communication subsystem between different Processing Units (PEs) in a SoC. PEs could be different elements such as CPU, memory, digital signal/analog signal processor etc. Different PEs performs specific tasks depending on the applications running on the chip. Different tasks need to exchange data information among each other, thus flits ( chopped packet with limited header information ) are generated by PEs. The flits are injected into the NoC by the proper interface and routed until reach the destination PEs. For the whole procedure, the NoC behaves as a packet switch network. Studies show that in general the information processing in the PEs only consume 60~\% energy while the remaining 40~\% are consumed by the NoC. More importantly, as the current network designing principle, the NoC capacity is devised to handle the peak load. This is a clear sign for energy saving when the network load is low. In our work, we considered to exploit Dynamic Voltage and Frequency Scaling (DVFS) technique, which can jointly decrease or increase the system voltage and frequency when necessary, i.e, decrease the voltage and frequency at low load scenario to save energy and reduce power dissipation. More precisely, we studied two different NoC architectures for energy saving, namely single plane chip and multi-plane chip architecture. In both cases we have a very strict constraint to be that all the links and transmitter/receivers on the same plane work at the same frequency/voltage to avoid synchronization problem. This is the main difference with many existing works in the literature which usually assume different links can work at different frequency, that is hard to be implemented in reality. For the single plane NoC, we exploited different routing schemas combined with DVFS to reduce the power for the whole chip. Our results haven been compared with the optimal value obtained by modeling the power saving formally as a quadratic programming problem. Results suggest that just by using simple load balancing routing algorithm, we can save considerable energy for the single chip NoC architecture. Furthermore, we noticed that in the single plane NoC architecture, the bottleneck link could limit the DVFS effectiveness. Then we discovered that multiplane NoC architecture is fairly easy to be implemented and it could help with the energy saving. Thus we focus on the multiplane architecture and we found out that DVFS could be more efficient when we concentrate more traffic into one plane and send the remaining flows to other planes. We compared load concentration and load balancing with different power modeling and all simulation results show that load concentration is better compared with load balancing for multiplan NoC architecture. Finally, we also present one of the the energy efficient MSR design technique, which permits the MSR to follow the day-night traffic pattern more efficiently with our on-line energy saving algorithm