BitMEX launches new index price protections and swap rates for BTC contracts

Crypto derivatives exchange BitMEX has announced the following price protections for its bitcoin-based indices on which the pricing of the company’s futures contracts are derived from.

As many are aware of, during the past weeks, many major exchanges have experienced issues with their banking relationships, including major USD exchange Bitfinex, and one exchange sent miscalculated prices. These prices caused liquidations on multiple platforms, including BitMEX, even though all affected traders were reimbursed from BitMEX funds.

BitMEX intends for the index to accurately represent asset prices on functioning, liquid exchanges.

The BitMEX team said, “…unfortunately, the landscape is shifting quickly. We expect more index changes to come as exchanges lose and regain their banking relationships.”

In preparation, BitMEX is instituting the following protections to all BitMEX calculated indices:

For bitcoin/fiat currency pair based contracts, the tolerance will be 25%. For Altcoin contracts, tolerance will be 50%. The tolerance is subject to change with notice.

Additionally, the following protection has been in place since launch:

BitMEX earlier this week announced that Coinbase and Bitstamp represent the new constitutions on its bitcoin price index.

The following examples below illustrate the protections in detail:

Example 1 (3-Exchange Index):

The index is equally weighted between exchanges A, B, and C. The initial price on exchanges A, B, and C is 100, and the tolerance is 25%. The median index price is 100.

The price observed on exchange C changes to 50. Exchange C will be removed, the index price will remain at 100, and the index will now be equally weighted between exchanges A and B.

Example 2 (2-Exchange Index):

Tolerance: 25%
Time 0:
Exchange A Price: 100
Exchange B Price: 100
Published Index Price: 100

Time 1:

Exchange A Price: 100
Exchange B Price: 50
New Calculated Index Price: 75
Last Published Index Price: 100
New Published Index Price: 100
Because the difference between the two exchange prices and the New Calculated Index Price is greater than 12.5% (Tolerance / 2), the Last Published Index Price will be used.

Time 2:

Exchange A Price: 50
Exchange B Price: 50
New Calculated Index Price: 50
Last Published Index Price: 100
New Published Index Price: 50
Because the difference between the two exchange prices and the New Calculated Index Price is less than 12.5%, the New Calculated Index Price will be used.

Example 3 (1-Exchange Index):

The index is made up only of exchange A. The price on exchange A moved from 100 to 50. Given that the tolerance is 25%, and exchange A’s price moved 50% (50 vs. 100), the index value remains at 100. If exchange A’s price changes to 51, the index value will still remain at 100. If exchange A’s price were to change to 80, the index value would become 80.

Example 4 (Downtime):

The index is equally weighted between exchanges A, B, C, and D. The API feed for Exchange D has been down for 15 minutes. Exchange D will be removed, and the index will now be equally weighted between A, B, and C. 5 minutes later, D begins responding and is reinstated.


The exchange also initiated bitcoin/dollar swap funding rate calculation changes. Due to the mentioned exchange disruptions, BitMEX says there has become no credible source for overnight USD and bitcoin lending rates.

The BitMEX bitcoin/USD Swap, XBTUSD, currently uses the Bitfinex overnight USD and bitcoin lending rate in the funding rate calculation. Effective today, 21 April 2017 12:00 UTC, the interest rate component of the funding rate calculation will be fixed at a positive 0.03% per day.

To arrive at this number, we calculated the average difference between the Bitfinex daily USD and bitcoin lending rates for a 12 month period ending 31 March 2017 to arrive at the positive 0.03% rate.

If the swap price does not trade at a premium or discount during a funding calculation period (currently 8 hours in length), longs will pay shorts 0.01%. This equates to a daily rate of positive 0.03%.

When the deposits and withdrawals of fiat and bitcoin are operating normally, BitMEX will select an appropriate exchange from which to source overnight USD and bitcoin rates.