It is convenient to believe that in a $4trillion per day market there is always enough liquidity to do what needs to be done. Unfortunately belief does not negate the reality that for every buyer there MUST be a seller or no transaction can occur. When an order is too large to transact at the current price, the price moves to the point where open interest is abundant enough to cover it. Every time you see price move a single pip, it means that an order was executed that consumed (or otherwise removed) the open interest at the current price. There is no other way that prices can move.
As we covered earlier, each bank lists on EBS how much and at what price they are willing to transact a currency. It is important to note that no Interbank participant is under any obligation to make a transaction if they do not feel it is in their best interest. There are no “market makers” on the Interbank; only speculators and hedgers.
Looking at an ECN platform or Level II data on the stock market, one can get a feel for what the orders on EBS look like. The following is a sample representation:
You’ll notice that there is open interest (Level II Vol figures) of various sizes at different price points. Each one of those units represents existing limit orders and in this example, each unit is $1million in currency.
Using this information, if a market sell order was placed for 38.4mil, the spread would instantly widen from 2.5 pips to 4.5 pips because there would no longer be any orders between 1.56300 and 1.56345. No broker, market maker, bank, or thief in the night widened the spread; it was the natural byproduct of the order that was placed. If no additional orders entered the market, the spread would remain this large forever. Fortunately, someone somewhere will deem a price point between those 2 figures an appropriate opportunity to do something and place an order. That order will either consume more interest or add to it, depending whether it is a market or limit order respectively.
What would have happened if someone placed a market sell order for 2mil just 1 millisecond after that 38.4 mil order hit? They would have been filled at 1.5630 Why were they “slipped”? Because there was no one to take the other side of the transaction at 1.56320 any longer. Again, nobody was out screwing the trader; it was the natural byproduct of the order flow.
A more interesting question is, what would happen if all the listed orders were suddenly cancelled? The spread would widen to a point at which there were existing bids and offers. That may be 5,7,9, or even 100 pips; it is going to widen to whatever the difference between a bid and an offer are. Notice that nobody came in and “set” the spread, they just refused to transact at anything between it.
Nothing can be done to force orders into existence that don’t exist. Regardless what market is being examined or what broker is facilitating transactions, it is impossible to avoid spreads and slippage. They are a fact of life in the realm of trading.