No Arabic abstract
Peer review (e.g., grading assignments in Massive Open Online Courses (MOOCs), academic paper review) is an effective and scalable method to evaluate the products (e.g., assignments, papers) of a large number of agents when the number of dedicated reviewing experts (e.g., teaching assistants, editors) is limited. Peer review poses two key challenges: 1) identifying the reviewers intrinsic capabilities (i.e., adverse selection) and 2) incentivizing the reviewers to exert high effort (i.e., moral hazard). Some works in mechanism design address pure adverse selection using one-shot matching rules, and pure moral hazard was addressed in repeated games with exogenously given and fixed matching rules. However, in peer review systems exhibiting both adverse selection and moral hazard, one-shot or exogenous matching rules do not link agents current behavior with future matches and future payoffs, and as we prove, will induce myopic behavior (i.e., exerting the lowest effort) resulting in the lowest review quality. In this paper, we propose for the first time a solution that simultaneously solves adverse selection and moral hazard. Our solution exploits the repeated interactions of agents, utilizes ratings to summarize agents past review quality, and designs matching rules that endogenously depend on agents ratings. Our proposed matching rules are easy to implement and require no knowledge about agents private information (e.g., their benefit and cost functions). Yet, they are effective in guiding the system to an equilibrium where the agents are incentivized to exert high effort and receive ratings that precisely reflect their review quality. Using several illustrative examples, we quantify the significant performance gains obtained by our proposed mechanism as compared to existing one-shot or exogenous matching rules.
This paper designs a market platform for Peer-to-Peer (P2P) energy trading in Transactive Energy (TE) systems, where prosumers and consumers actively participate in the market as seller or buyer to trade energy. An auction-based approach is used for market clearing in the proposed platform and a review of different types of auction is performed. The appropriate auction approach for market clearing in the proposed platform is designed. The proposed auction mechanism is implemented in three steps namely determination, allocation and payment. This paper identifies important P2P market clearing performance indices, which are used to compare and contrast the designed auction with different types of auction mechanisms. Comparative studies demonstrate the efficacy of the proposed auction mechanism for market clearing in the P2P platform.
A distributed machine learning platform needs to recruit many heterogeneous worker nodes to finish computation simultaneously. As a result, the overall performance may be degraded due to straggling workers. By introducing redundancy into computation, coded machine learning can effectively improve the runtime performance by recovering the final computation result through the first $k$ (out of the total $n$) workers who finish computation. While existing studies focus on designing efficient coding schemes, the issue of designing proper incentives to encourage worker participation is still under-explored. This paper studies the platforms optimal incentive mechanism for motivating proper workers participation in coded machine learning, despite the incomplete information about heterogeneous workers computation performances and costs. A key contribution of this work is to summarize workers multi-dimensional heterogeneity as a one-dimensional metric, which guides the platforms efficient selection of workers under incomplete information with a linear computation complexity. Moreover, we prove that the optimal recovery threshold $k$ is linearly proportional to the participator number $n$ if we use the widely adopted MDS (Maximum Distance Separable) codes for data encoding. We also show that the platforms increased cost due to incomplete information disappears when worker number is sufficiently large, but it does not monotonically decrease in worker number.
We propose measurement integrity, a property related to ex post reward fairness, as a novel desideratum for peer prediction mechanisms in many applications, including peer assessment. We operationalize this notion to evaluate the measurement integrity of different mechanisms in computational experiments. Our evaluations simulate the application of peer prediction mechanisms to peer assessment---a setting in which realistic models have been validated on real data and in which ex post fairness concerns are quite salient. We find that peer prediction mechanisms, as proposed in the literature, largely fail to demonstrate measurement integrity in our experiments. However, we also find that certain mechanisms can be supplemented with realistic parametric statistical models to improve their measurement integrity. In the same setting, we also evaluate an empirical notion of robustness against strategic behavior to complement the theoretical analyses of robustness against strategic behavior that have been the main focus of the peer prediction literature. In this dimension of analysis, we again find that supplementing certain mechanisms with parametric statistical models can improve their empirical performance. Even so, though, we find that theoretical guarantees of robustness against strategic behavior are somewhat noisy predictors of empirical robustness. As a whole, our empirical methodology for quantifying desirable mechanism properties facilitates a more nuanced comparison between mechanisms than theoretical analysis alone. Ultimately, we find there is a trade-off between our two dimensions of analysis. The best performing mechanisms for measurement integrity are highly susceptible to strategic behavior. On the other hand, certain parametric peer prediction mechanisms are robust against all the strategic manipulations we consider while still achieving reasonable measurement integrity.
In practice, most mechanisms for selling, buying, matching, voting, and so on are not incentive compatible. We present techniques for estimating how far a mechanism is from incentive compatible. Given samples from the agents type distribution, we show how to estimate the extent to which an agent can improve his utility by misreporting his type. We do so by first measuring the maximum utility an agent can gain by misreporting his type on average over the samples, assuming his true and reported types are from a finite subset---which our technique constructs---of the type space. The challenge is that by measuring utility gains over a finite subset of the type space, we might miss type pairs $theta$ and $hat{theta}$ where an agent with type $theta$ can greatly improve his utility by reporting type $hat{theta}$. Indeed, our primary technical contribution is proving that the maximum utility gain over this finite subset nearly matches the maximum utility gain overall, despite the volatility of the utility functions we study. We apply our tools to the single-item and combinatorial first-price auctions, generalized second-price auction, discriminatory auction, uniform-price auction, and second-price auction with spiteful bidders.
In the classical secretary problem, one attempts to find the maximum of an unknown and unlearnable distribution through sequential search. In many real-world searches, however, distributions are not entirely unknown and can be learned through experience. To investigate learning in such a repeated secretary problem we conduct a large-scale behavioral experiment in which people search repeatedly from fixed distributions. In contrast to prior investigations that find no evidence for learning in the classical scenario, in the repeated setting we observe substantial learning resulting in near-optimal stopping behavior. We conduct a Bayesian comparison of multiple behavioral models which shows that participants behavior is best described by a class of threshold-based models that contains the theoretically optimal strategy. Fitting such a threshold-based model to data reveals players estimated thresholds to be surprisingly close to the optimal thresholds after only a small number of games.