Context

(Bitstamp:BTCUSD 5m)

Bitcoin saw a huge price spike today of $1100+ within the span of 45 minutes. (One of) the biggest derivatives exchanges, Bitmex, saw as much as $0.6B of trading within the hour, with Bitfinex also seeing 38k Bitcoin (~$280M) trading in the same 1h period.

I've seen a lot of theories going around recently relating to exchange manipulation and stop loss/ liquidation hunting by exchanges and I think its best to look into how margin trading works and the issue with some of the claims, along with today's dramatic events.

Margin Trading and Derivatives Explained

As Bitcoin trading has developed, there have been more and more offerings of margin trading by exchanges, allowing people to borrow value to trade with, to amplify profits (or losses) before repaying the loan at a later date. Many traders use this to make different strategies more viable, such as scalping or swing trading.
As well as its use for leverage, margin/ derivatives also allow shorting. This gives the opportunity to trade the decline of a market rather than having to sit in cash and wait. So how does it work?

Spot markets

In a spot market, the underlying assets that are going to be traded have to be borrowed during the trade and paid back (with interest) to the lender once the trade is closed. Exchanges such as Bitfinex manage this through a Peer to Peer lending system, where the loan is provided by other users on the platform.

The exchange has to ensure that the loan will always be paid back to the lender, as such, positions have a liquidation threshold. If the value of the traded asset were to swing too far against the trader, their account wouldn't have sufficient funds to be able to pay back the value of the loan. For this reason, we have an initial margin level and a maintenance margin level.

The initial margin limit (30% for Bitfinex) means that traders can't take on unreasonably large positions, so sudden market swings won't drive the account into negative value. The maintenance margin limit (15% for Bitfinex) is where the exchange will margin call (forcefully close) the position to avoid going into negative balance.

For example, if you were to take out a 3x leverage long on Bitcoin vs USD, your initial margin is 33%. Then, if Bitcoin were to drop 18% (33% - 15%) you would be margin called, forcefully closing the position to avoid further losses.

When a position is margin called, it's traded into the regular market to close the position. If you are long on Bitcoin vs USD, the position will be sold off to get back the USD needed to pay off the loan. In this case, there is no point at which the exchange is taking on your position, it is simply forcing you to close it into the market so you can pay off your loan to the lending user.

Derivatives markets

Derivatives markets, such as Bitmex, work slightly differently. The underlying asset being traded doesn't change hands to take on a position. Instead each side of the trade takes opposing sides of a futures contact. Derivatives are helpful as a trading tool, as you only need to have a fraction of the equity of a contract, rather than taking out a loan of the asset.

The normal rules of initial margin and maintenance margin still apply. But, instead of paying back a P2P loan, its to protect the exchange from negative balance. If an account balance became negative, there would be no way for the exchange to get back the difference ,since Bitmex is funded anonymously in Bitcoin. As such, it needs a good mechanism to avoid excessive losses.

Bitmex does differ from Bitfinex, as the exchange will take on the position during a margin call. This is part of their "liquidation engine", which then closes the position into the market. The maintenance balance of the position is also taken to offset the loss of the liquidation engine as it closes the position. Any profit/ loss is added to the "insurance fund".

This system is required on Bitmex due to the high leverage they offer to traders, meaning that their is a high probability a losing trade could result in a negative balance. Any negative balance is paid off by the insurance fund. The insurance fund is not a conspiracy for the exchange to take your money, it is a simple fact that the margin calling system will not always be able to close positions in time during large market swings, so needs a cushion to avoid negative balances.

Short squeeze and margin cascade

Now, onto today's series of events. Looking at the BTCUSD chart, the red line shows Bitfinex margin shorts and the green line shows margin longs. Prior to the spike to $8069, margin shorts were at record highs of almost 41k Bitcoin. Then, as the price shot up, the shorts were rapidly liquidated.
Side note: I believe the margin data provided here is slightly delayed, as the raw data shows the cascading descent in margin shorts lining up better with the increase in price.

As the first shorts started to get liquidated, they were forced to buy into the market, driving up the price. This liquidated some more positions, forcing them to rapidly buy too, hitting the limit of yet more positions. This cascading effect shot the price into the sky as positions got forcefully closed. Margin shorts went from 39k Bitcoin at 11:30 (BST) to <29k Bitcoin at 12:30 (BST), over 10k Bitcoin in shorts closed within an hour.

People will try give many explanations for this overhang in shorts or the events leading up to the short squeeze. The squeeze was certainly a risk that I overlooked in my own trading, but I was fortunate enough not to have any open positions at the time. Short squeezes are a reality that people have to watch out for when trading any asset (although not often on this scale).

Manipulation and conspiracies

I'm hoping to address some of the issues I see in a post that's been going around a lot recently, which claimed that exchanges themselves were involved in stop-loss hunting to try to "extract a higher market fee" from traders when they get liquidated.

However, by definition, each trade has a market maker and a market taker, meaning that the exchange will get the same fee per volume either way (assuming no tiered fee structure), as one side will always be paying the taker fee. While there is a potential for an exchange be using margin calls as a means to increase their total trading volume, it seems like a rather roundabout method to try to extract relatively small value while potentially driving a way a significant portion of their clients. Surely an exchange would look to boost revenue through other means, such as new services and trading pairs before looking towards market manipulation on such a scale. Exchanges themselves also aren't brokers, they are the platform to allow different parties to trade, rather than being the market maker of each trade.

While stop-loss/ margin hunting does happen to a degree, it is unlikely that the exchanges themselves would stand to gain much from it. Instead, stop-loss hunting is an activity of institutions or "whales", who make a profit by accumulating a position at a lower price before pushing the market into a short squeeze and selling into the margin cascade. This requires an entity to be tactically building up an exposure before shifting the market in their favour.

While it isn't impossible that the operators of exchanges are involved in stop-loss hunting as part of a separate scheme, the exchange itself and its mechanisms of liquidation stands to make little profit on such action with the potential to drive away a lot of customers. It makes little sense for an exchange itself to be involved, as the financial incentives don't align.

Disclaimer

I will do my best to give unbiased, objective analysis, but I can make no promises about my accuracy.
All posts are based on my personal opinions and ideas and do not constitute professional financial investment advice.

Edit 13/04/18 01:19:
Rewrote final few paragraphs as it appears I misinterpreted the original article.