This discovery was a major factor in Arrow winning the Nobel Prize in Economics. Range voting satisfies all three criteria, accomplishing the "impossible"!

Let's check that in slow-mo: There is no dictator — that is, there exists no single range voter "Joe Stalin" who, no matter what the other voters say, always gets it his way. If every voter rates A above B, then A's summed-score and hence average score will be higher than B's. So the finish-order will rank A above B. Jane Voter's score for C in no way affects her scoring of A and B, which are totally independent scoring decisions made by that voter. Hence A's and B's averages and hence finish-order are in no way affected by how any and all voters rate C. And range voting is not the only voting system accomplishing the "impossible"; many others, such as trimmed-mean range voting which we recommend for judging figure-skating events, also do so.

How can this be?

## Arrow's Impossibility Theorem Definition

The explanation is simple. Arrow, when he made his theorem, made a definition of what a "voting system" was. His theorem only applies to voting systems that obey his definition. The trouble is that in my opinion Arrow made a silly definition.

## Book Review | The Arrow Impossibility Theorem

One reason it is silly is that, according to Arrow's definition, range voting is "not" a voting system at all. It sure looks and feels like a voting system. It inputs votes and it elects a winner. But according to Arrow's definition, it isn't a voting system. It is pretty easy to prove voting systems "impossible" if, as step one, you define a lot of voting systems as not being voting systems.

The true lesson of Arrow's theorem is more than anything else, in my opinion that you should stay away from voting systems based on rank-order ballots. Analysis of why Arrow didn't like range voting. Warren D. Smith pointed this out in , and Claude Hillinger at about the same time.

### Is There a Best Procedure? Arrow’s Impossibility Theorem

A few years later John C. Lawrence went further than them, making an especially strong criticism of Arrow: based on a close look at Arrow's words, Lawrence contends Arrow actually did briefly consider range voting, but dismissed it due to a mental mistake.

Much earlier than any of these people, economist John C. Harsanyi had pointed it out in the s shortly after Arrow's work appeared. Harsanyi later was awarded the Nobel Prize, but, despite that, his point about Arrow's theorem for some reason remained largely ignored and unknown. For example, you can read about how also Nobel Laureate Eric Maskin apparently remained ignorant of this as of There also are many more papers and books about this, e.

Kenneth J. Hamilton, Albert Rees, and Harry G. Johnson, The University of Chicago Press and other places. The theorem is constructed to resolve the question of whether there is any mathematical procedure for amalgamating individual preferences that results in a collectively rational preference ordering of all the possible outcomes. The theorem requires that individuals be permitted to have any rational preference ordering over alternatives, that there not be a single dictator whose preference over a single pair of alternatives holds for the group decision, that the collective ranking over outcomes remains unchanged if one of the alternatives ceases to be considered, and that a unanimous preference over a pair of outcomes implies a collective preference over that pair.

These requirements are generally regarded as beyond controversy. The theorem proves that, given these minimal assumptions, it is impossible to construct any procedure that results in a collectively rational expression of individual desires. Though highly technical in its statement, the theorem has important implications for philosophies of democracy and political economy. The theorem rejects the notion of a collective democratic will, whether derived through civic deliberation or construed by experts who paternalistically apply knowledge of what is best for a population.

The theorem also denies that there could be objective basic needs or universal criteria that any procedure for collective decision making should recognize, such as minimal nutrition standards or human rights.

### Kenneth Arrow's Impossibility Theorem

Impossibility theorem. Info Print Cite. Submit Feedback. Because plurality rule, the Borda count, singular transferable vote, instant runoff, and approval voting all reduce to majority rule for two candidates and an odd number of voters, there needs to be some other way to evaluate and compare election procedures. Can one determine an election procedure to satisfy a collection of reasonable properties?

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And, what are the properties? Kenneth Arrow.

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At 51, Arrow was the youngest person ever to receive the Prize. Consider the shopper that tries on a pair of shoes.

## Three brief proofs of Arrow’s Impossibility Theorem

The clerk indicates that the shoes are available in brown and black. The customer decides to get the shoes in black. The clerk finds a pair of the shoes in mahogany and lets the customer know.