International Conference “Governing for the Future” (Bucharest, Romania, 9-12 June, 2016) © Medimond . T609F0025 191 Status quo bias and social choice rules, evidence from a laboratory experiment Vlăducu A. 1 1 Department of Political Science, National School of Political Science and Public Administration (ROMANIA) andreivladucu@snspa.ro Abstract There are many procedures that turn individual preferences into collective decision. Generically they are known as social choice rules. Simple majority rule is one of the best known, and is often used when individuals face political, economic or social decisions. Other social choice rules, which are not used in mass political election, but prove to be efficient in other contexts (especially in the corporate sector), are approval voting and Borda count. Beside this, they are considered to be more easily adapted to the modern context of choice and better responding to behaviours like strategic voting. On the other hand, status quo bias is a common effect from heuristics and biases approach (a theoretical subfield of behavioural economics) affecting human behaviour, sometimes with disturbing results. In this paper we test the effect of status quo bias on the three social choice rules mentioned above through a laboratory experimental design. The main conclusion is that simple majority rule is significantly affected by status quo bias, while approval voting and Borda count are not. A direct implication of this conclusion is that individuals seem to prefer simple majority because it represents the default of elections. Keywords: Status quo bias, simple majority rule, approval voting, Borda count, psychological experiments, behavioural economics. 1 Introduction Individuals are faced with choices in every moment of their lives, whether we are talking about the election of the president, taking a new job or the way they build and aggregate criteria by which universities are ranked. To be able to make such decisions we need practical mechanisms that turn individual preferences into group decisions, known as social choice rules. There is a wide range of social choice rules used in the context of political, economic or social decisions. When speaking of social choice rules we understand a set of procedures that stipulates: a) how an individual preference for an alternative is translated into a vote, and b) how individual decisions are aggregated into collective decisions [1]. Majority rule, in its various forms, is the most spread social choice rule by which decisions are taken, especially when talking about the political competition [2]. In this experiment we examine a specific form of majority rule - simple majority rule (SMR), which stipulate that the winning alternative is the alternative who gets most votes, without necessarily touching 50% +1 of the total votes. Additionally, there are a variety of experimental rules, which are not used in the mass election, but prove to be very practical when decisions must be made at the level of institutions or professional associations [2, 3]. Approval voting and Borda count are considered one of the most viable candidates to the title of social choice rules through which decisions can be made at the level of mass elections. There are a series of arguments in their favour like: they are simple, intuitive or they have the capacity to make individuals to express sincere preferences and avoid strategic behaviour. When a decision is made using approval voting (AV), this situation implies that each individual can approve (select, elect etc.) how many alternatives he/she wishes from the set of available alternatives. The winning alternative will be the one who obtains the highest number of approvals. Borda count (BC) implies that every individual has the opportunity to rank all the alternatives available in the context of an election and give them a number of points, depending on her rank. For example, if we need to choose between three alternatives, the alternative that is first in the hierarchy gets three points, the second two points and third one gets one point. The winning alternative is that who obtain the highest score comparing with all other. Nowadays there is a common ground that different social choice rules used in the same decisional situation could produce different results. Evidence of this phenomenon is to be finding in [4-8]. A natural question that rose from this situation is which of these different outcomes is correct and which criteria we use to determine what social choice rules we