Also efficiency can be relative to a trader even if everyone only trades on public information because in
I’ll be blunt and start here, as it is an important mistake I see made a lot. I think a lot of people misunderstand what market efficiency refers to. It has nothing to do with individual trader behavior. You could be seeking out the worst investments, that wouldn’t matter to the question of how efficient the market is. Market efficiency is just about the price. To the extent the price accurately reflects available information (or the underlying fundamental value) the market is efficient. An individual traders behavior is entirely irrelevant.
Also, efficiency doesn’t equate to “good” so it can be a bit misleading. You could say roulette is 95% efficient, since the price is just off by ~5% of the underlying value (which can be ascertained by available information). But there isn’t any way for you to reliably capture that 5%, it is off because of value captured by the house. And, like prediction markets, roulette is a negative sum game.
Isn’t a natural conclusion then that in reality prediction markets are not completely efficient?
Sure, hence the “if” in my original comment. If you are doing it because you like to gamble, that’s fine. Risk hedging also theoretically makes sense, but isn’t currently how the markets are being used in any meaningful aense (and as mentioned runs dirextly contrary to how proponents like Hanson often suggest they should be used).
If you think the average traders are predictably irrational it should be possible to take their money and enrich the platform in the platform in the process. That seems like a bad thing and a good reason to advocate against prediction markets. Negative sum games are not exactly great for the economy, and anyone with altruistic views should view negative sum games as definitionally net negatives, I would argue.
Proponents of prediction markets generally argue they are efficient markets. If they aren’t, the utility generally claimed to exist isn’t there.
Subsidy can come in another form, a player can spend money trying to elicit information so that they can use the information somewhere else.
Spending money doesn’t gain information. As I mentioned in my other comment. There is no additional price discovery function you can access to by placing a bid or ask on a prediction market. To the extent the market has that value, it is independent of your transactions.
I wouldn’t say anyone is really discussing perfect efficiency. You could reasonably say roulette is a fairly efficidnt market, the price accurately reflects 95% of the value.
There isn’t really value you can reliably, fairly make off them (otherwise someone like Jane Street would probably have scooped it up). You may be able to make money in some, but odds are more likely than not you are wrong and the juice isn’t worth the squeeze.
Yes, and if that is the case, your chances are greater than not that no matter how intelligent you are if that is true using a prediction market will lose you money.
What, though? The main valid arguments for utility i see—risk management and price discovery—are not how the platforms are being used or not good reasons to trade (on current platforms) respectively. To be clear, I think there are valid arguments for utility in potential, but what is currently being promoted by proponents in extant markets doesn’t match the potential utility.
In theory, maybe. In reality, doesn’t happen on any current platforms. To the extent they adopt automatic market makers, those market makers act more as bookies, providing liquidity only at prices in excess of reasonable fair odds. Some play money platforms use automatic market makers designed to encourage price discovery (which Hanson has advocated for) but I am not aware of any large prediction markets that do so.
They have costs and there still is time value issues (to be truly net-zero, the total value of any position on average would have to appreciate by the risk-free rate + a risk premium), so it is still a net negative sum in that sense.
But I was talking from the perspective of a person trading, not society as a whole.
I don’t necessarily think so. Like, a lot of scams are zero sum, but I would say scamming people is still wrong (even in cases where it might not legally be fraud). Taking advantage of people being gullible or gamblers is generally something I would not view favorably, and where there is a net loss (as is the case with, say, gambling at a casino) my default is to take a rather skeptical view.
In the case of equity, there is the fairly valid claim that it determines how equity is allocated, and by definition more efficiently allocating equity leads to greater economic product and therefore a net positive (and equity tends to increase in value above the risk free rate). Traders in prediction markets aren’t really doing that; they are not capital markets.