Exploiting Social Influence to Control Elections Based on Scoring Rules

Online social networks are used to diffuse opinions and ideas among users, enabling a faster communication and a wider audience. The way in which opinions are conditioned by social interactions is usually called social influence. Social influence is extensively used during political campaigns to advertise and support candidates. Herein we consider the problem of exploiting social influence in a network of voters in order to change their opinion about a target candidate with the aim of increasing his chance to win/lose the election in a wide range of voting systems. We introduce the Linear Threshold Ranking, a natural and powerful extension of the well-established Linear Threshold Model, which describes the change of opinions taking into account the amount of exercised influence. We are able to maximize the score of a target candidate up to a factor of $1-1/e$ by showing submodularity. We exploit such property to provide a $\frac{1}{3}(1-1/e)$-approximation algorithm for the constructive election control problem. Similarly, we get a $\frac{1}{2}(1-1/e)$-approximation ratio in the destructive scenario. The algorithm can be used in arbitrary scoring rule voting systems, including plurality rule and borda count. Finally, we perform an experimental study on real-world networks, measuring Probability of Victory (PoV) and Margin of Victory (MoV) of the target candidate, to validate the model and to test the capability of the algorithm.Comment: Extended abstract published in Proceedings of the 18th International Conference on Autonomous Agents and MultiAgent Systems (AAMAS 2019). Paper published in Proceedings of the 28th International Joint Conference on Artificial Intelligence (IJCAI 2019

Multi-Winner Election Control via Social Influence

In an election, we are given a set of voters, each having a preference list over a set of candidates, that are distributed on a social network. We consider a scenario where voters may change their preference lists as a consequence of the messages received by their neighbors in a social network. Specifically, we consider a political campaign that spreads messages in a social network in support or against a given candidate and the spreading follows a dynamic model for information diffusion. When a message reaches a voter, this latter changes its preference list according to an update rule. The election control problem asks to find a bounded set of nodes to be the starter of a political campaign in support (constructive problem) or against (destructive problem) a given target candidate $c$, in such a way that the margin of victory of $c$ w.r.t. its most voted opponents is maximized. It has been shown that several variants of the problem can be solved within a constant factor approximation of the optimum, which shows that controlling elections by means of social networks is doable and constitutes a real problem for modern democracies. Most of the literature, however, focuses on the case of single-winner elections. In this paper, we define the election control problem in social networks for "multi-winner elections" with the aim of modeling parliamentarian elections. Differently from the single-winner case, we show that the multi-winner election control problem is NP-hard to approximate within any factor in both constructive and destructive cases. We then study a relaxation of the problem where votes are aggregated on the basis of parties (instead of single candidates), which is a variation of the so-called "straight-party voting" used in some real parliamentarian elections. We show that the latter problem remains NP-hard but can be approximated within a constant factor

Fear Not, Vote Truthfully: Secure Multiparty Computation of Score Based Rules

We propose a secure voting protocol for score-based voting rules, where independent talliers perform the tallying procedure. The protocol outputs the winning candidate(s) while preserving the privacy of the voters and the secrecy of the ballots. It offers perfect secrecy, in the sense that apart from the desired output, all other information -- the ballots, intermediate values, and the final scores received by each of the candidates -- is not disclosed to any party, including the talliers. Such perfect secrecy may increase the voters' confidence and, consequently, encourage them to vote according to their true preferences. The protocol is extremely lightweight, and therefore it can be easily deployed in real-life voting scenarios

Prices Matter for the Parameterized Complexity of Shift Bribery

In the Shift Bribery problem, we are given an election (based on preference orders), a preferred candidate $p$, and a budget. The goal is to ensure that $p$ wins by shifting $p$ higher in some voters' preference orders. However, each such shift request comes at a price (depending on the voter and on the extent of the shift) and we must not exceed the given budget. We study the parameterized computational complexity of Shift Bribery with respect to a number of parameters (pertaining to the nature of the solution sought and the size of the election) and several classes of price functions. When we parameterize Shift Bribery by the number of affected voters, then for each of our voting rules (Borda, Maximin, Copeland) the problem is W[2]-hard. If, instead, we parameterize by the number of positions by which $p$ is shifted in total,then the problem is fixed-parameter tractable for Borda and Maximin,and is W[1]-hard for Copeland. If we parameterize by the budget, then the results depend on the price function class. We also show that Shift Bribery tends to be tractable when parameterized by the number of voters, but that the results for the number of candidates are more enigmatic

Corruption in UK local government: the mounting risks

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Organized Business, Political Regimes and Property Rights across the Russian Federation

This article explores the inter-relationship of collective action within the business community, the nature of the political regime and the security of firms’ property rights. Drawing on a pair of surveys recently administered in Russia, we present evidence that post-communist business associations have begun to coordinate business influence over state actors in a manner that is sensitive to regional politics. A firm’s ability to defend itself from government predation and to shape its institutional environment as well as its propensity to invest in physical capital are strongly related to both its membership in a business association and the level of democratization in its region. Of particular note, the positive effect of association membership on securing property rights increases in less democratic regions. The evidence, that is, suggests that collective action in the business community substitutes for democratic pressure in constraining public officials.

Do Elections Affect the Composition of Fiscal Policy?

This paper investigates the impact of elections on the level and composition of fiscal instruments using a sample of 19 high-income OECD countries that can be characterized as developed, established democracies during the period 1972-1999. We find that elections shift public spending towards current and away from capital expenditures. Moreover, although we find no evidence for an electoral cycle for government deficit and expenditures, we do find a negative effect of elections on revenue. Our results indicate that the fall in revenue in election periods is attributed to a fall in direct taxation. The decomposition of our electoral dummy suggests that fiscal manipulation seems to be concentrated shortly before the elections. Finally, when we distinguish among predetermined and endogenous elections we find that the above results apply only for the predetermined electoral periods while endogenous elections seem to increase the budget deficit and to leave the composition of fiscal policy unaffected.political budget cycles, elections, composition of fiscal policy, quality of public expenditure

Complexity Dichotomies for Unweighted Scoring Rules

Scoring systems are an extremely important class of election systems. We study the complexity of manipulation, constructive control by deleting voters (CCDV), and bribery for scoring systems. For manipulation, we show that for all scoring rules with a constant number of different coefficients, manipulation is in P. And we conjecture that there is no dichotomy theorem. On the other hand, we obtain dichotomy theorems for CCDV and bribery problem. More precisely, we show that both of these problems are easy for 1-approval, 2-approval, 1-veto, 2-veto, 3-veto, generalized 2-veto, and (2,1,...,1,0), and hard in all other cases. These results are the "dual" of the dichotomy theorem for the constructive control by adding voters (CCAV) problem from (Hemaspaandra, Hemaspaandra, Schnoor, AAAI 2014), but do not at all follow from that result. In particular, proving hardness for CCDV is harder than for CCAV since we do not have control over what the controller can delete, and proving easiness for bribery tends to be harder than for control, since bribery can be viewed as control followed by manipulation

Deliberative Democracy in the EU. Countering Populism with Participation and Debate. CEPS Paperback

Elections are the preferred way to freely transfer power from one term to the next and from one political party or coalition to another. They are an essential element of democracy. But if the process of power transfer is corrupted, democracy risks collapse. Reliance on voters, civil society organisations and neutral observers to fully exercise their freedoms as laid down in international human rights conventions is an integral part of holding democratic elections. Without free, fair and regular elections, liberal democracy is inconceivable. Elections are no guarantee that democracy will take root and hold, however. If the history of political participation in Europe over the past 800 years is anything to go by, successful attempts at gaining voice have been patchy, while leaders’ attempts to silence these voices and consolidate their own power have been almost constant (Blockmans, 2020). Recent developments in certain EU member states have again shown us that democratically elected leaders will try and use majoritarian rule to curb freedoms, overstep the constitutional limits of their powers, protect the interests of their cronies and recycle themselves through seemingly free and fair elections. In their recent book How Democracies Die, two Harvard professors of politics write: “Since the end of the Cold War, most democratic breakdowns have been caused not by generals and soldiers but by elected governments themselves” (Levitsky and Ziblatt, 2018)

Election Manipulation on Social Networks: Seeding, Edge Removal, Edge Addition

We focus on the election manipulation problem through social influence, where a manipulator exploits a social network to make her most preferred candidate win an election. Influence is due to information in favor of and/or against one or multiple candidates, sent by seeds and spreading through the network according to the independent cascade model. We provide a comprehensive study of the election control problem, investigating two forms of manipulations: seeding to buy influencers given a social network, and removing or adding edges in the social network given the seeds and the information sent. In particular, we study a wide range of cases distinguishing for the number of candidates or the kind of information spread over the network. Our main result is positive for democracy, and it shows that the election manipulation problem is not affordable in the worst-case except for trivial classes of instances, even when one accepts to approximate the margin of victory. In the case of seeding, we also show that the manipulation is hard even if the graph is a line and that a large class of algorithms, including most of the approaches recently adopted for social-influence problems, fail to compute a bounded approximation even on elementary networks, as undirected graphs with every node having a degree at most two or directed trees. In the case of edge removal or addition, our hardness results also apply to the basic case of social influence maximization/minimization. In contrast, the hardness of election manipulation holds even when the manipulator has an unlimited budget, being allowed to remove or add an arbitrary number of edges.Comment: arXiv admin note: text overlap with arXiv:1902.0377