Vote trading: An economic and ethical perspective

Thomas Goh


May 18th, 2018

Thomas Goh looks closer at the practice of vote trading by elected representatives, drawing on social choice theory and political philosophy.

On 21 November 2009, a provision was added to the Senate Health Care Bill which increased Medicaid funding to states recovering from a major disaster. As it so happens, this provision only affected Louisiana which received $300 million in subsidies from this amendment.[1] The amendment was added in order to secure the vote of Mary Landrieu, a Democrat from Louisiana, and it was the last vote required in order to move the bill out of committee. This sort of trading happens quite in America, and to a lesser extent in Australia and is commonly known as ‘logrolling’.

Strictly defined, logrolling refers to a practice where one elected representative trades a decisive vote on a policy they support in return for someone else’s decisive vote on an issue they really care about. Vote trading is usually frowned upon as it is seen as prioritising the preferences of special interest groups at the expense of the public. It also gives the impression of a lack of integrity when politicians backflip to vote for issues they don’t support. However, there are times where logrolling produces desirable results such as passing essential policy or avoiding tyranny of the majority by giving minorities a voice.

To explore whether logrolling is desirable we will need to explore what sort of impact it has on the community and to do this we shall rely the tool of Social Cost-Benefit analysis. This analysis rests on three basic assumptions: firstly, is possible to measure social utility for a group of individuals; secondly, a politician will only vote for a policy if the utility for their constituents is positive; and lastly, if the social benefit outweighs the social cost, then a policy is in the public interest.

For example, let’s consider a situation where the government is deciding whether to build a Library or a Dam. To keep it simple, imagine just three representatives in parliament: A, B and C who fully understand the preferences of their constituents to be as follows:

Library Dam Both
Voter A 20 -5 20 – 5 = 15
Voter B -12 15 -12 +15 = 3
Voter C -10 -15 -10 – 15 = -30
Social Benefit -2 -5 15 + 3 – 30 =-7

Note: The actual value of the numbers is not important, only their relative size

The first important thing to note from this table is that there is a majority (2/3) of votes against both the Library and the Dam. In addition to this, each policy has a negative social benefit meaning that the socially optimal outcome is for both policies to fail. This is of course the expected outcome if no vote trading is allowed as there is a majority against both policies.

However, if we allow for the trading of votes, both policies pass. This is because although Voter A and B both individually get a small positive utility from both policies passing, the general public takes a loss.

This highlights one of the core issues in logrolling; when there is a conflict between the preferences of the public and the preferences of constituents, who should politicians vote in favour of? The answer to this depends on who the politician is representing. Should they only representing those who vote for them? Or should they represent the entire public? John Thrasher (philosophy lecturer at Monash) provides a moral argument for the former through describing a ‘thin account of representation’. This account is fairly simple. Representatives ought to vote in a way that furthers the interests/preferences of their constituents. When this conflicts with a larger political unit (such as state or country) then the representative should still vote in favour of their constituents, taking into account how the larger political situation will affect their constituents over time.[2] If we accept this reasoning, then we have a good reason to believe that politicians actually have a duty to engage in vote trading when it is beneficial for their constituents.

Of course, this does not resolve all our issues with logrolling and there are many more questions we need to answer. For example: Is it even possible to collate the interests of every single person in an electorate into a single preference? Should we be encouraging behaviour that reduces overall social utility? Ultimately, there are good reasons both for and against vote trading. What is important is not that we all come to the same conclusion, but that we acknowledge, and think about the conflicting ideals in vote trading. By doing so we become better informed citizens which strengthens our democracy and empowers us to hold politicians accountable.


[1] Milbank, D. (2009) ‘Sweeteners for the South’, Washington Post, 22 November. Available from:

[2] Thrasher, J. (2016). The Ethics of Legislative Vote Trading. Political Studies, 64(3), pp 614-629. DOI: 10.1111/1467-9248.12205

The views expressed within this article are those of the author and do not represent the views of the ESSA Committee or the Society's sponsors. Use of any content from this article should clearly attribute the work to the author and not to ESSA or its sponsors.

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