Budget-Feasible Mechanism Design for Non-Monotone Submodular Objectives: Offline and Online

The framework of budget-feasible mechanism design studies procurement auctions where the auctioneer (buyer) aims to maximize his valuation function subject to a hard budget constraint. We study the problem of designing truthful mechanisms that have good approximation guarantees and never pay the participating agents (sellers) more than the budget. We focus on the case of general (non-monotone) submodular valuation functions and derive the first truthful, budget-feasible and $O(1)$-approximate mechanisms that run in polynomial time in the value query model, for both offline and online auctions. Prior to our work, the only $O(1)$-approximation mechanism known for non-monotone submodular objectives required an exponential number of value queries. At the heart of our approach lies a novel greedy algorithm for non-monotone submodular maximization under a knapsack constraint. Our algorithm builds two candidate solutions simultaneously (to achieve a good approximation), yet ensures that agents cannot jump from one solution to the other (to implicitly enforce truthfulness). Ours is the first mechanism for the problem where---crucially---the agents are not ordered with respect to their marginal value per cost. This allows us to appropriately adapt these ideas to the online setting as well. To further illustrate the applicability of our approach, we also consider the case where additional feasibility constraints are present. We obtain $O(p)$-approximation mechanisms for both monotone and non-monotone submodular objectives, when the feasible solutions are independent sets of a $p$-system. With the exception of additive valuation functions, no mechanisms were known for this setting prior to our work. Finally, we provide lower bounds suggesting that, when one cares about non-trivial approximation guarantees in polynomial time, our results are asymptotically best possible.Comment: Accepted to EC 201

USING ACTIVITY THEORY FOR MODELLING TRANSFORMATIVE DIGITAL LEARNING

In support of ongoing educational transformation in post-Soviet nations, this article positions activity theory (in the tradition of Engeström) as a framework for modelling changes towards innovative forms of collabo-rative, fully online digital learning. A strength of activi-ty theory is that it adopts a holistic socio-technical per-spective in which teachers, learners, technologies, peda-gogical values, roles/identities and rules/cultures are considered together as interdependent elements of col-lective activity. An illustrative example is offered to model a current and envisioned (target) activity system. In addition, a few considerations to guide research are offered. These include an emphasis on measuring the general readiness of students and teachers, and the need to explore gender divides. The goal is to help envision program transformations towards online learning at two partner universities as part of Ukrainian and Lat-vian, government-funded projects

Fracturing Falsehoods: Multiplexity in Windsor-Detroit\u27s Organized Crime Networks 1900-1933

In the Windsor-Detroit borderland, the period between 1900 and 1933 was characterized by the nation-state’s increasing legislative ability to enact interventionist measures to produce a regulated border. While the criminalization of alcohol in 1916 and 1920 by both the Canadian and U.S. governments respectively, enabled policy-makers to establish a transnational boundary, its implementation resulted in the production of legal asymmetries which forced the expansion and integration of the illicit economy into legitimate society through organizational actors and their respective enterprises. Employing Chris M. Smith and Andrew V. Papachristos concept of multiplex ties in criminal organizations in conjunction with Willem van Schendel’s theory of illicit flows in borderlands, the paper seeks to reconstruct Harry Low’s Windsor-based organized crime network to determine how his syndicate employed multiplexity as an operational mechanism to circumvent the newly defined legislative boundaries between licit and illicit to make products flow during prohibition. By analyzing how the growth of organized crime was imbricated in the state process to control the flow of goods and people in the borderland; therefore, undermines the presentation of the Windsor-Detroit border as a static reciprocal relationship in which the illicit economy operated during the first third of the 20th century

On the Tree Conjecture for the Network Creation Game

Selfish Network Creation focuses on modeling real world networks from a game-theoretic point of view. One of the classic models by Fabrikant et al.[PODC\u2703] is the network creation game, where agents correspond to nodes in a network which buy incident edges for the price of alpha per edge to minimize their total distance to all other nodes. The model is well-studied but still has intriguing open problems. The most famous conjectures state that the price of anarchy is constant for all alpha and that for alpha >= n all equilibrium networks are trees. We introduce a novel technique for analyzing stable networks for high edge-price alpha and employ it to improve on the best known bounds for both conjectures. In particular we show that for alpha > 4n-13 all equilibrium networks must be trees, which implies a constant price of anarchy for this range of alpha. Moreover, we also improve the constant upper bound on the price of anarchy for equilibrium trees

Feeding the Empire: Grain, Warfare, and the Persistence of the British Atlantic Economy, 1765-1815

The importance of staple agriculture in the development of the modern world can hardly be overstated. The connotations surrounding the word “bread” and the phrase “staff of life” bear witness to the close association between the availability of grain and the overall well-being of western societies. It is not a coincidence that bread is both an important religious symbol and a causal force in the maintenance or collapse of entire societies. This dissertation aspires to provide a clearer understanding of the leading place of overseas trade in the American economy in the late eighteenth and early nineteenth centuries by showing how European war restored colonial trade relationships and reintegrated the US into trans-Atlantic and international economic exchanges led by grain exports. By challenging the assumption that the rupture of the American Revolution led naturally to economic separation, this project argues that material forces and long-standing cultural ties were more powerful than politics in shaping the contours of the British Atlantic world in the nineteenth century. Assessing the political economy of the grain trade deepens our understanding of the late colonial and early republican US. Grain was also vital to the British Atlantic and British North American economy of this era. The inherent difficulties of overcoming national, imperial, and war-divided historiographies conceals grain from our easy gaze. Mistaken ideas of periodization and politically inspired limitations to historical assessments ultimately hide connections that were fundamental at the time. The availability of surplus grain, particularly from the mid-Atlantic colonies in what would become the United States, were essential to the viability of societies around the British Atlantic. Simply stated, without food society ceases to function. Ideology falls to the wayside, plantations cease production, populations collapse, and long-distance warfare becomes impossible. Examining the availability of food products, the laws enabling or limiting trade, and the extraordinary (and sometimes illegal) steps taken to ensure that the staff of life was available to fuel social development was crucial to the rise of Anglo-American power in a tumultuous Age of Atlantic Revolutions whose political drama should not completely eclipse its economic foundations

Envy, Regret, and Social Welfare Loss

Incentive compatibility (IC) is a desirable property for any auction mechanism, including those used in online advertising. However, in real world applications practical constraints and complex environments often result in mechanisms that lack incentive compatibility. Recently, several papers investigated the problem of deploying black-box statistical tests to determine if an auction mechanism is incentive compatible by using the notion of IC-Regret that measures the regret of a truthful bidder. Unfortunately, most of those methods are computationally intensive, since they require the execution of many counterfactual experiments. In this work, we show that similar results can be obtained using the notion of IC-Envy. The advantage of IC-Envy is its efficiency: it can be computed using only the auction's outcome. In particular, we focus on position auctions. For position auctions, we show that for a large class of pricing schemes (which includes e.g. VCG and GSP), IC-Envy ≥ IC-Regret (and IC-Envy = IC-Regret under mild supplementary conditions). Our theoretical results are completed showing that, in the position auction environment, IC-Envy can be used to bound the loss in social welfare due to the advertiser untruthful behavior. Finally, we show experimentally that IC-Envy can be used as a feature to predict IC-Regret in settings not covered by the theoretical results. In particular, using IC-Envy yields better results than training models using only price and value features