Why ever use a market order?

Question

I've read all the explanations online. Use market to fill quick, regardless of price. But... How that is that different from a sell limit of 0 or a buy limit of infinity? (Right, in practice things can't so far without halting but the general idea stands.)

Why world anyone take the (albeit minuscule) risk of a market order (aka no limit limit order)? What's the point? Why not simply use limit orders, set to, say 10% or 20% of current? Do they execute differently in most cases where the prices don't take huge jumps quickly?

What am I missing? I've heard some users are charged less for a market order. Is that still true and causing this technically unneeded order type to be available and encouraged to all?

PabTorre · Accepted Answer

What you are saying is a very valid concern. 
After the flash crash many institutions in the US replaced "true market orders" (where tag 40=1 and has no price) with deep in the money limit orders under the hood, after the CFTC-SEC joint advisory commission raised concerns about the use of market orders in the case of large HFT traders, and concerns on the lack of liquidity that caused market orders that found no limit orders to execute on the other side of the trade, driving the prices of blue chip stocks into the pennies.

We also applaud the CFTC requesting comment regarding whether it is
  appropriate to restrict large order execution design that results in
  disruptive trading. In particular, we believe there are questions
  whether it is ever appropriate to permit large order algorithms that
  employ unlimited use of market orders or that permit executions at
  prices which are a dramatic percentage below the present market price
  without a pause for human review

So although you still see a market order on the front end, it is transformed to a very aggressive limit in the back end. However, doing this change manually, by selling at price 0 or buying at 9999 may backfire since it may trigger fat finger checks and prevent your order from reaching the market.  For example BATS Exchange  rejects orders that are priced too aggressively and don't comply with the range of valid prices. 
If you want your trade to execute right now and you are willing to take slippage in order to get fast execution, sending a market order is still the best alternative.

Victor · Answer

The purpose of a market order is to guarantee that your order gets filled. If you try to place a limit order at the bid or ask, by the time you enter your order the price might have moved and you might need to keep amending your limit order in order to buy or sell, and as such you start chasing the market. A market order will guarantee your order gets executed.

Also, an important point to consider, is that market orders are often used in combination with other orders such as conditional orders. For example if you have a stop loss (conditional order) set at say 10% below your buy price, you might want to use a market order to make sure your order gets executed if the price drops 10% and your stop loss gets triggered, making sure that you get out of the stock instead of being stuck with a limit order 10% below your buy price whilst the stock keeps falling further.

Jasper · Answer

The original poster's concern is valid.  Sometimes, market orders do get executed at seemingly ridiculous prices.

In addition to Victor's reasons for using a market order, sometimes a seller does not care how low the price is.  For example, after a company goes broke, its stock continues to trade for a while.  This allows shareholders to realize their losses for tax purposes, and allows short-sellers to close out their positions.  A shareholder who is trying to realize a 10 dollar per share loss for tax purposes probably does not care whether he gets 10 cents per share or 0.001 cents per share, so a sell-at-market order makes sense.

lionel319 · Answer

I think it all boils down to which is your priority.

if it's a limit order

you are being guaranteed that you will never pay more than this amount
but you are not guaranteed of getting the stock

if it's a market order

you are being guaranteed (well, in a way) of getting the stock
but u are not guaranteed of getting it at the ask price

So it all depends.
People that want the stock sooOoooo badly will definitely go for the market order.

vic · Answer

I don't think you're missing anything. Many modern trading systems actually warn you when trying to enter a market order, asking if you are sure that you wouldn't prefer to set a limit. I fully agree with you that it is usually just better to define a limit even 20% higher than just doing a market trade.

Let me give you some examples when you still might prefer to use a market order instead of a limit:

In a highly liquid market with very small spreads, for example blue chips on NYSE. Unless you want to rule out your own typing mistake, a limit order won't give you any benefits.
As Victor already said, when you really want to fill an order no matter the price. For example, you just want to sell your share when the market opens, even if the price will be a lot lower than the last closing.

But even in those two examples a (wide) limit order might just be the safer thing to do.

So, what it really comes down to is speed: A market order has no other criterias to be defined, is thus entered faster and saves you a few seconds that might be crucial.

Why ever use a market order?

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