Bullish Exchange Joined CoinDesk’s Bitcoin Price Index

Bullish became a contributing exchange to the CoinDesk Bitcoin Price Index, or XBX, through an implementation period ending at 4 p.m. Eastern on October 27, 2024. The addition expanded the benchmark’s venue set from five exchanges to six and changed an important reference price used by institutional bitcoin products.

CoinDesk Indices had announced the scheduled change on October 11 after completing its quarterly review of single-digital-asset price indices. Its notice listed Bullish as an addition to XBX and specified no deletion. After implementation, XBX drew data from Coinbase, Kraken, Bitstamp, Crypto.com, LMAX Digital and Bullish.

The change mattered because XBX was more than a display price. Grayscale Bitcoin Trust, traded on NYSE Arca as GBTC, used the index price to calculate net asset value per share at 4 p.m. New York time on each valuation date. Grayscale Bitcoin Mini Trust, traded as BTC, used the same benchmark. Adding a venue therefore altered the market-data inputs behind the daily valuation of two exchange-traded products holding bitcoin.

A benchmark change, not a bitcoin trade

CoinDesk Indices said the October modifications would be implemented gradually over the 24 hours ending at 4 p.m. Eastern on October 27. That phased window limited the disruption that could result from adding a new contributing exchange all at once.

The index provider’s methodology used recent trading information from eligible venues rather than treating every exchange quotation equally. Regulatory materials describing XBX said constituent exchanges were weighted in proportion to trailing 24-hour liquidity, with adjustments for price variance and inactivity. Consequently, Bullish’s inclusion did not mean it received one-sixth of the index or a permanent fixed weight.

The surviving October 11 announcement did not disclose Bullish’s starting weight, the trading volume used to establish eligibility or the numerical minimum-liquidity threshold it satisfied. Grayscale’s subsequent SEC filing confirmed only that Bullish met the index provider’s minimum liquidity requirement.

No bitcoin price, percentage return or trading-volume reaction is attributed to the October 27 change. The reviewed records establish a benchmark-input modification, not an identifiable purchase or sale of bitcoin. Because October 27 was a Sunday, the practical effect on Grayscale’s business-day net asset value calculations would appear in subsequent valuation periods.

The wider quarterly review

Bullish was one of several venues added across CoinDesk’s single-asset index family. The same implementation introduced new contributors for indices covering Cardano, bitcoin cash, EOS, litecoin, solana, uniswap, stellar lumens and tezos. No exchange was removed from any of the nine indices listed in the announcement.

That broader review showed how institutional crypto benchmarks depend on continuing venue assessment. A reference rate can diversify price discovery across exchanges, but additional inputs do not eliminate exchange outages, anomalous trades, liquidity changes or governance risk. Index users must still understand which venues contribute and how their weights are determined.

Ownership required disclosure

Bullish Global had acquired CoinDesk in November 2023. The acquiring company said CoinDesk—which included its indices business—would operate as an independent subsidiary within Bullish Group. That ownership relationship was publicly known before the October 2024 index review and is material context when a Bullish-operated exchange becomes a benchmark contributor.

The reviewed records do not establish improper influence over the eligibility decision. They establish that CoinDesk Indices conducted a scheduled review, added Bullish under its stated liquidity criterion and announced the change approximately two weeks before implementation. Independence and conflict-management controls remained appropriate subjects for benchmark users to examine.

Later confirmation and a date discrepancy

Grayscale filed a Form 8-K on October 31 confirming that the change was effective October 27. Its quarterly report repeated the October 27 date. Some later Grayscale annual filings instead described the addition as occurring on October 28, creating a one-day inconsistency in the retrospective record.

For this reconstruction, the contemporaneous CoinDesk implementation notice and Grayscale’s event-specific filing control: the phase-in ended at 4 p.m. Eastern on October 27, 2024. The defensible conclusion is narrow. Bullish became an XBX contributor, expanding the benchmark’s venue coverage without proving that the change materially moved the index price or improved investment outcomes.