BitMEX indices are composite, meaning that they are calculated using a number of data sources. BitMEX currently uses 9 constituents: Binance, Bitstamp, Bittrex, Coinbase, Gemini, Huobi, Itbit, Kraken, Poloniex.
Aiming to be representative of the underlying asset’s market consensus price, each BitMEX index is calculated as a weighted average of the Last Price for each constituent exchange. Index prices are calculated and published every 5 seconds. The index weights are shown in the table below. The constituents and index weights are reviewed and updated on a quarterly basis. Changes will be announced on the BitMEX website, on the BitMEX blog and via the BitMEX RSS feed, with three weeks notice before implementation. The BitMEX “NEXT” indices will be published at that time to track the hypothetical price of the indices with the new weights.
BitMEX Index Weights, assuming no constituent exchanges have been excluded due to Index Protection Rules, last updated 27 December 2019 at 12:00:05 UTC. For current weights incorporating any exclusions refer to the relevant Composite Index Breakdown.
The BitMEX index weights will be updated next on 27 March 2020 at 12:00:05 UTC.
The weights for BitMEX indices will be updated immediately after each quarterly futures expiry, with updates based on three months of constituent exchange volume data. The date range for data will be from 00:00 UTC on the first day of the month for the expiring quarterly future to 00:00 UTC on the first day of the month for the next quarterly future.
For example, at 12:00:05 UTC on 25 December 2020, updated weights will be used to calculate the BitMEX indices. These weights will be announced on 4 December 2020 and will be based on constituent exchange volume data from 00:00 UTC on 1 September 2020 to 00:00 UTC on 1 December 2020. These weights will apply to the BitMEX “NEXT” indices from 4 December 2019.
The BitMEX “NEXT” indices (eg. .BXBT_NEXT) will display the hypothetical index prices with the new weights. These index prices will line up with the normal index prices once the announced weights are live (ie .BXBT_NEXT and .BXBT will have the same price). “NEXT” indices are not used for valuation or settlement, they are used to display hypothetical index prices with new weights before implementation.
BitMEX “NEXT” Index Weights, assuming no constituent exchanges have been excluded due to Index Protection Rules, last updated on 6 December 2019. For current weights incorporating any exclusions refer to the relevant Composite Index Breakdown.
These “NEXT” index weights are computed using three months of constituent exchange volume data from 00:00 UTC on 1 September 2019 to 00:00 UTC on 1 December 2019.
The next update for BitMEX “NEXT” index weights will be on 7 March 2020.
On 17 October 2019 at 00:00 UTC the Last Prices on the constituent exchanges were:
These Last Prices are multiplied by the weights to give
|Last Price x Weight||2143.698||3552.329||495.337||335.958||1468.800|
The sum of Last Price x Weight across all constituents was 7996.123. The sum of Weights across all constituents was 100%.
So the .BXBT_NEXT price was 7996.123 / (100%) =7996.12 (rounded to nearest USD cent).
The BitMEX index weights are computed using volume data obtained directly via API connection from each of the constituent exchanges listed above. Proprietary mechanisms are used to identify malformed and anomalous data, which is discarded. The index weight calculation removes constituents with insufficient trade volume. For the avoidance of doubt, and in accordance with BitMEX Terms of Service, HDR Global Trading Limited (operator of the BitMEX trading platform) accepts no responsibility for the accuracy of any volume (or other) data received from any exchange and used to calculate the value of any BitMEX index and excludes all liability for any claimed losses arising in connection with its calculation and publication of any such index.
For further information see the individual index and index weights pages:
BitMEX uses several methods to maintain reliable connections to the constituent exchanges. As a fallback the following tests and actions are used:
1 If a constituent exchange is unresponsive, the previous price is used.
2 If a constituent exchange’s price is unchanged for 15 minutes, the constituent is removed from the index until it is operational.
3 (a) For indices with 3 or more constituents: if a constituent price differs from the median constituent price for that index by 25% or more, it is excluded from the index calculation. The constituent returns to the index when its price differs from the median by less than 25%.
3 (b) For indices with only 2 constituents: if a constituent price differs from the median constituent price for that index by 12.5% or more, the last calculated index price will be used. The index is updated once its price differs from the median by less than 12.5%.
3 (c) For an index with only 1 constituent: if the constituent price is 25% away from the last calculated index price, the last calculated index price will be used. The index is updated once the constituent price differs from the last calculated index price by less than 25%.