
- Mathematician Kenneth Arrow proved that no ranked voting system can be completely fair with three or more candidates.
- Common systems like first-past-the-post and ranked-choice voting are deeply flawed and can produce irrational outcomes.
- Alternatives like approval voting offer promise, but democracy may never be mathematically perfect.
The Math Behind Voting: Why Democracy Can't Be Perfect
Let’s be real: most of us don’t think about math when we vote. We just pick a name, check a box, and hope our side wins. But what if I told you that democracy—the very system we rely on to reflect the will of the people—is mathematically flawed from the ground up?
No, this isn’t some dramatic political hot take. It’s a legit, Nobel Prize-winning discovery that proves something wild: there’s no perfect way to vote when three or more choices are involved. The math says democracy, at least as we practice it, is doomed to be a little irrational.
Let’s break that down.
🗳️ First-Past-the-Post: Easy, but Broken
This is the classic “vote for one candidate, most votes wins” system. It sounds simple and clean—and it’s the one used in most U.S. states, the UK, and many former British colonies.
But here’s the kicker: it frequently gives power to parties that didn’t get the majority of votes. In fact, in the UK’s last century of elections, that happened 19 times out of 21.
And then there’s the spoiler effect. Remember the 2000 U.S. election? Ralph Nader’s Green Party campaign likely cost Al Gore the presidency, even though most Nader voters preferred Gore over Bush. That’s because voters could only pick one person, even if their loyalties were split.
So people start voting strategically, not honestly. That leads to two-party systems (thanks, Duverger’s Law), polarization, and the sense that your real preference doesn’t matter. Yikes.
🔄 Ranked-Choice Voting: Better… Right?
Enter Instant Runoff Voting (IRV), aka ranked-choice voting. Voters rank candidates. If no one gets a majority, the lowest-ranked candidate is dropped and their votes are redistributed based on second choices. Repeat until someone wins.
Sounds way more fair, right?
Well… sometimes. In practice, weird stuff happens. Like, a candidate doing worse in early rounds can actually end up winning the election. That’s not just annoying—it’s mathematically broken.
This is known as non-monotonicity, and it's just one of the many head-scratchers that make even smarter voting systems glitchy.
🔁 Condorcet's Beautiful, Broken Idea
In the 1700s, French mathematician Marquis de Condorcet proposed a “fair” system: the winner should be the one who’d beat every other candidate in a one-on-one contest.
Logical? Yes. Practical? Not quite.
Because guess what? Condorcet’s Paradox shows that preferences can loop endlessly. Imagine three friends trying to choose dinner:
- You prefer burgers > pizza > sushi.
- Friend 2 prefers pizza > sushi > burgers.
- Friend 3 goes sushi > burgers > pizza.
Now:
- 2 out of 3 prefer sushi over burgers.
- 2 out of 3 prefer pizza over sushi.
- And 2 out of 3 prefer burgers over pizza.
Boom—endless loop. No clear winner.
🧠 Arrow's Impossibility Theorem
Here’s where it gets wild. In 1951, economist Kenneth Arrow proved something now known as Arrow’s Impossibility Theorem. He outlined five criteria that any fair voting system should meet:
- Unanimity: If everyone prefers A to B, society should too.
- No Dictatorship: One vote shouldn't override everyone else's.
- Consistency: The system should produce the same result every time for the same inputs.
- Transitivity: If A > B and B > C, then A > C.
- Independence of Irrelevant Alternatives: Adding a third choice shouldn’t mess with how A and B are ranked.
Sounds reasonable, right?
Arrow proved it’s impossible to satisfy all five with any ranked voting system involving three or more candidates. It just can't be done. He earned a Nobel Prize for this mind-melting revelation.
So yeah, democracy, in its purest mathematical sense? Impossible.
👍 So, Now What?
Don’t give up yet.
While ranked systems are flawed, rating systems offer hope. Think approval voting—tick all the candidates you’re okay with. The one with the most approval wins.
Simple. Fair. No spoilers. And it turns out this system was used way back in papal elections and is still used by the UN.
Even Arrow himself, late in life, admitted rated systems might be the best shot we've got.
🌈 A Bit of Hope
There's also something called the Median Voter Theorem. If voters fall along a spectrum (say left to right politically), the person who appeals to the middle—the median—tends to win. That’s not perfect, but it does help avoid chaos and loops.
And maybe that's the takeaway: we don’t need perfect, we need better. Recognizing the flaws means we can fix—or at least improve—the game.
🎤 So… Is Democracy a Lost Cause?
Nope. It’s just complicated.
Think of it like this: your GPS might not always take the fastest route, but it gets you where you’re going better than a paper map. Democracy’s kind of like that. It’s not flawless, but it still beats the alternatives.
So yes, mathematically, democracy may be “impossible.” But striving to make it better? That’s still possible—and totally worth it.
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