A persistent bias in prediction markets is pricing very non likely events as slightly more likely than they are. ie; a 1% event priced at 4%, etc, because people like to bet long shots.
Whether there is enough of a predictable bias there to snag enough low return high probability bets to beat the vig and not shift the markets I have not looked into in any way,but it is a known bias with them.
The real money to be made in prediction markets is being the ones with the actual knowledge which is arguably why they are useful and why for some topics, people find them abhorrent.
It might be a bias in terms of the probability of events, but I'm not so sure this is a market inefficiency in terms of actual trading strategy. If true odds are 1% and the event is priced at 4%, I can sell NO for a 3% edge... but lose 100% once out of a hundred. Doesn't seem worth it!
I think you get less return on investment for the same absolute edge in percentage points. A 1% event priced at 4% gets you a 3/96 = ~3.1% return. A 53% event priced at 50% gets you a 6% return. You nearly double your returns by investing in the latter market even though they're both off by 3 percentage points.
If the market isn't resolving soon, the small return might not be worth it.
Even if a cut isn't taken and there aren't other inefficiencies, any money tied up in long-term predictions is earning 0% instead of whatever the current risk-free rate of return is.
IBKR relentlessly advertises on the radio, so I’m aware that on their scheme you earn an interest like incentive coupon for every day you hold open the position.
Happy IBKR customer here. ForecastTrader has absolutely horrific liquidity outside of maybe 30-40 large contracts. The rest is all market makers that only offer 10-100 or so shares at each price point before bumping up a penny or two. No knock on IBKR as a whole, but you can't even effectively buy on most events or outcomes without slippage eating away your entire edge, and forget about real serious positions above a few grand entirely outside of those 30-40 big contracts.
It doesn't seem like it's strictly true that they don't charge trading fees.
From their docs, it looks like they charge fees to bet "takers" (as opposed to makers), but exclude the geopolitical and world-events markets where they don't charge fees.
I have to imagine that may be related to some of the blow-back towards prediction markets about profiting on topics like war & their potential for manipulation.
Given it sounds like the bot bets everywhere other than sports, many of those categories would likely have fees in this case.
Polymarket charges “taker” fees (people removing liquidity by matching listed orders) on most markets. Geopolitics markets are exempt. A portion of the collected fees then get redistributed to “makers” (people who provide liquidity by listing orders for others to match). Presumably the rest of these fees make up polymarket’s revenue.
Which is essentially also providing a platform for making the book for the other platform, on which 'bookie fees' are charged, but Polymarket itself only keeps a certain cut of it, for facilitating but not actually book-making.
If the average no costs less than 73 cents, but the 73% of all polymarkets resolve to No, that would imply that the nothing-ever-happens strategy here is profitable. Are you claiming that it is profitable? Or are one of those premises incorrect?
Edit: conversely, if the average no costs _more_ than 73 cents, but the 73% of all polymarkets resolve to No, that would imply that an everything-always-happens strategy is profitable (neglecting slippage)
> Edit: conversely, if the average no costs _more_ than 73 cents, but the 73% of all polymarkets resolve to No, that would imply that an everything-always-happens strategy is profitable (neglecting slippage)
Or just the bid-ask spread; price no at 73.25 and yes at 27.5 and you have a profitable but theoretical mid-market price.
From what I've seen and tested, it's been profitable, for the reason you said. Variance and other caveats caused me to not pursue it further. https://news.ycombinator.com/item?id=47754918
It doesn't matter if a vast majority of people are not rational economic actors. It only takes 1 rational actor with enough capital to take the other side of all the bad bets, and the market will be priced correctly even if the other 99 people are irrational.
'Enough' [capital] is doing a lot of work in that sentence. In the limit of a one-sided irrational market, the 'rational actor' would need to take the other side of every open transaction.
Well, if the price would be incorrectly set, then bots like this one would make money, which would in sufficient time cause the market to adapt and the average price would change so the bot doesn't work.
That doesn't matter so much when it happens in a place where people can make money from other people's irrationality. Even if there are a bunch of irrational people placing bad bets on uncommon future events, rational people looking to make a buck will take the other side of that bet, until the price is sensible.
The alternative would be that there's a bunch of free money sitting there waiting for someone to decide to pick it up, and nobody is, not even you.
The whole premise of prediction markets is that the few people whose perception do match outcomes make bets to push the money-weighted average perception toward outcomes. If perceptions still don't match outcomes at that point, average return is 0 minus transactions, with high variance.
Yes, but I always found that objection a bit silly. It's like pointing out that real cows are obviously not perfect spheres nor do they live in a vacuum.
> [...] if prices perfectly reflected available information, there is no profit to gathering information, in which case there would be little reason to trade and markets would eventually collapse.[2]
That's a stupid way to formulate this. Markets wouldn't "collapse". They would get slightly less efficient until equilibrium is restored to where arbitragers can make enough money to keep prices at that level of efficiency.
Maybe not "collapse" in a the sense of going to zero but if there was no profit to trading, then the quant trading industry would not exist, trading profits would collapse.
Meanwhile Two Sigma is hiring alpha quants to be AI research scientists at $250k starting salary + bonuses.
Even if we're just talking about the HFT/sell-side, there clearly exist various anomalous inefficiencies that can be exploited.
As I said, if we woke up this morning and prices were magically efficient in an idealised sense, at most a few quants would go home and retire early, and tomorrow we'd be back at the level (in-) efficiency that allows people to be market makers.
I bet the average price for a no bet across these markets is 73 cents.