Actually, in our technoligical terms, simulating quantum mechanics would require an insane amount of compute. Quite the opposite of what you're suggesting. One method would be the sum over histories, which means integrating over every possible way of getting to each possible outcome. Of course, if our universe is being simulated the stimulator wouldn't necessarily be constrained by our technology. But your argument was that the simulator was trying to save cycles, whereas classical mechanics is far easier to simulate.

Except, a man with the face of Jesus who says odd things is not at all unusual. Whereas a piece of entirely indestructible toast would be impossible to ignore and doesn't fit any of our current physics.

The fact is that by the evidence available to them, they would have no reason to assume a god. One would be neither explanatory, nor helpful to them. A god would be pointless. Unless, of course, the programmer takes part in the virtual world, changing things at will. But then they would have evidence, wouldn't they?

Suppose a screw manufacturer cut their price by halving their profit, but as a result sells 10 times as many screws. You wouldn't call that an ambiguous comparison, would you? It's exactly the same with shares. Market makers cut their per share profit, but increased their volume. As a result shares are much cheaper to trade, and more trading takes place. The big difference with shares is you're not buying in the first market (from the manufacturer), you're buying aftermarket, so the buyer needs a way to find the seller and they need to agree on a price. The most efficient means yet found for this is the market maker. Any more efficient way woukd naturally supplant the market maker buy undercutting their profit.

If you submit market orders, you are paying the bid ask spread. It's per share, so it's completely unambiguous. Put it this way: suppose the theoretical value of XYZ is $98.7633 then the best bid will be $98.76 and the best offer will be $98.77. If you submit a market order to buy a 100 lot, you'll be matched at $98.77, paying $0.0067 per share to the market maker, totalling $0.67 for the lot. But, you don't have to do that. You could instead submit a limit order to buy 100 at $98.76. And you'd likely get filled after a fairly short time. So: 1 people CHOOSE to pay the spread. So they must see a benefit. 2 your broker likely charges more in fees. The benefit is quality of fill... you'll get filled instantly at the nbbo in the first case. In the latter case you may not get filled at all... the price may change. These small fluctuations are next to meaningless to a long term investor, but they keep the markets efficient and risk down. There's much less risk to owning a stock when you know you can sell at within a penny of its value at a moment's notice. As for "other efficiencies" occurring at the same time, it's simply false. HFTs shrunk spreads by competing with the specialists, who used to keep the spreads at 25c in many cases. The specialist was unable to compete with 1c spreads -their profits dried up. This isn't theoretical, it's fact. HFTs are also supremely good at arbitrage, to a degree that prices are always very very close to ideal. HFTs are better for your trading than your broker. You seem genuine, unlike many here, so I hope you continue to discuss this.

That was a completely valueless comment. It did nothing to furthur the discussion. It didn't present any viewpoint or evidence. You merely call me a thief and state that I wouldn't accept any proof if you did present it. I'm asking for any shred of evidence for other's benefit... because I know you have none - as evidenced by your lack of ability to present it. I'm the expert in this discussion, so it should be obvious why I keep asking. Some people have had genuine questions for me about HFT, and want to learn. You clearly want to remain ignorant. So be it.

Oh, and it's not whether YOU screw up, it's when the exchange screws up. E.g. if a match occurs outside the NBBO. And yes, in that case you CAN request a do over.

Reread my post. KNIGHT DID NOT GET A DO OVER. Some trades were busted, and that's only in clear cut cases. But at the end of the day Knight lost half a billion dollars. Those trades settled.

So it's simply the efficiency of scale that you object to? Even knowing that before HFT, the market makers used to collude to keep the spreads at a quarter, and now (since HFTs compete) spreads are mostly a cent? And you still haven't mentioned any harm. Btw all orders would go thru a specialist even before HFT, so it's not "a trade" vs "all trades". Last thing: if you don't want to pay the market maker, simply join the best ask or best bid, and don't pay the spread. It's entirely your choice when you submit your order. Of course, your broker will still charge fees, but you can't blame that on HFT.

Others have said it, so it must be true? Lewis book is the only one I'm aware of, and I haven't read it yet. Public investigations? Show me. I responded to the comment you linked to, btw. More haymaking. You really don't understand any of this stuff, yet feel entitled to spout other people's unsubstantiated nonsense. You have yet to come up with a single solid piece of support for your accusations.

I know all about payment for order flow (although we don't do it). Brokers have been allowed to match orders without sending them to an exchange forever. This is a simple extension of that. Why is it a problem? Regulations mean that the order must trade at the NBBO whether it goes to the exchange or not. The customer gets the best price. All trades and their times have to be submitted to regulators to ensure the rules are being followed. This is more haymaking. Unless, of course, you have evidence that some company is not following these rules... then I suggest you contact the authorities. But you don't, do you?

Everything you've said so far is demonstrably false, and now you claim you have proof. Where is it? Which company? Put up or shut up. Even if some HFTs had entered into some bad behaviors (and you've presented no evidence), that doesn't show that HFT is itself necessarily bad. What is it about HFT that you think is wrong? You can't answer because you don't actually understand it. You don't know what we do or how we interact with marketplaces. For some reason your ignorance doesn't stop you from making wild unsupported claims.

There isn't any way for an HFT company to see an order "on its way" to an exchange. HFT companies CAN see the trades and react, but that's public info, and anyone can react. That story you are referring to is nonsense, the times quoted were quite within reasonable transmission times. Even if they weren't it would mean somebody on the inside had leaked information to a trader. You can't blame HFT for that.

The market was in favor of the big players long before HFT. In fact HFTs tend to be small shops. The two I've worked for started with 2 people. So basically the reverse of what you claim is true. Studies show that in the whole, HFT improves stability. The occasional mistake is less likely to have a big impact since circuit breakers were introduced. I doubt you can find evidence that HFT reduces stability. As for HFT creating irrational highs, it's utter crap. HFT makes money from small fluctuations. Large price swings are caused by big events. Investment still works as it ever did - ask your broker. As for leaching, how does any trading make money? We buy and sell and profit. The only difference is competition has driven down margins and latency. Are you from Salem?

I'm talking about independent studies. Even some where the researchers were expecting the reverse result. Regardless, what you're describing isn't correct. Orders are executed in time order. There isn't a way for am HFT company to "get in front" once they "see a big trade". I've been working in HFT for nearly 8 years. I actually know how this stuff really works. We don't manipulate markets, or jump the queue, or any of the usual accusations. We'd be in jail. We use strategies that are basically the same as those that existed before computers. It's simply that competition has driven down latency, and margins, but increased efficiency and liquidity.