[cma]

>as a market participant I largely do not care about the implementation of any given market makers risk configs

Why? It could severely hurt market liquidity (which everyone claims is so important) if there is a mistake that sparks a panic.

> was not as good at lowering the cost of risk as opposed to getting fast

Can you reword this a bit? I don't understand what you are saying.

> I think that any artificial slowing of the market is likely to have really bad unintentional issues.

Can you give some examples?

> One approach that appeals to me is to remove the sub-penny rule that is artificially propping up spreads.

This would be a decent thing to do, it would take some money out of market making, reducing the returns fueling the latency arms race a bit. Lower returns would also give less justification for some of the risks that are taken today.

A transaction tax would help in a similar way, but work more broadly against other high volume, low latency, low value traders. Index-to-underlyings arbitragers (maybe not the best example; sub-penny would decimate (hurr) them as well), etc.

[kasey_junk]

> Why? It could severely hurt market liquidity (which everyone claims is so important) if there is a mistake that sparks a panic.

Because we've seen what happens when a very major market maker blows their risk configs, it is a headlines day but the market largely recovers quickly. I'm more interested in systematic risk and I believe that any "fix" to the speed issue in HFT is likely either just going to shuffle advantage from one group to another or have unintended consequences.

> Can you reword this a bit? I don't understand what you are saying.

It was more risky to be slow than to use a central (and assumedly better) risk system. At least that was the implicit lesson learned from a market maker not using their own systems. I understand trading incentives enough to realize that might have been short term thinking trumping long term thinking, but I'd rather adjust the incentives there as well (long term bans from trading for risk limit violators maybe?)

Further, I want market makers to be able to be innovative with some of their risk controls, as I believe that it could lead to better risk controls more broadly.

> Can you give some examples?

The most common response that people trot out to "fix" HFT is to introduce batch auctions. I believe that this a) won't remove the incentives to play speed games and b) will make it harder for market makers to price spreads appropriately leading to them making them more expensive.

A transaction tax is similar. I view transaction taxes as pass throughs that will largely be paid by non-speculative investors. That is, we actually largely don't care (I don't think) about the number of transactions, so why would we use a tax to discourage them? Lets discourage what we actually want to discourage (I'm not sure what that is by the way).

> Index-to-underlyings arbitragers

I'm not so sure. In the short term they and market makers would get wrecked, but I believe quickly they would adjust (or go out of business) and the pricing models would be better for it, and spreads would go even lower.

[cma]

> Because we've seen what happens when a very major market maker blows their risk configs, it is a headlines day but the market largely recovers quickly.

Knight Capital, for example, was just at the threshold where they were effectively able to be bailed out. Nothing guaranteed it. Other large market makers are owned by banks and are essentially risking capital reserves. We haven't hit a scenario where a hit to one participant has had systemic effects, but that doesn't mean it isn't a risk.

> It was more risky to be slow than to use a central

From this and some of your other comments I see you are taking the stand that every market transaction is about pricing risk, and so talking about risk separately isn't ever a useful concept. Maybe you can say that under lots of abstraction, but it seems to make it unnecessarily difficult to communicate with people who speak of it with the normal meaning.

>innovative with some of their risk controls, as I believe that it could lead to better risk controls more broadly

Decentralizing risk controls in the way I mentioned is strictly worse in every metric but latency. Or at least there was no other explicit reason why we did it.

>The most common response that people trot out to "fix" HFT is to introduce batch auctions. I believe that this a) won't remove the incentives to play speed games and b) will make it harder for market makers to price spreads appropriately leading to them making them more expensive.

I'm not necessarily proposing batches, but a significant fraction of daily trading volume already goes through the opening and closing auctions every day. When stocks are halted and re-opened, they go through auctions as well in many exchanges, just opening right back up conceivably leads to worse pricing than the auction system with published imbalances.

My point about market hours, weekends, and holidays, is that all this stuff is based more on tradition and precedent than any kind of goals. Participants that trade through microsecond latency advantages are extracting a tax on everyone else. A transaction tax takes out a lot of these opportunities, and can be used for something more productive than the waste heat result of running a bunch of spin locks in a datacenter.

[kasey_junk]

> Participants that trade through microsecond latency advantages are extracting a tax on everyone else.

I completely disagree with this and have seen no proof of it one way or the other.

One data point that convinces me lacking any proof, is that spreads are tightest in the products with the highest competition for latency. It seems that speed is bringing the tax down not up.