From https://am.coinbase.com/ https://am.coinbase.com/: >* Coinbase Index Fund will invest in assets in proportion to their relative market capitalizations and

From https://am.coinbase.com/ https://am.coinbase.com/: >* Coinbase Index Fund will invest in assets in proportion to their relative market capitalizations and rebalance annually on January 1st. This strategy will track Coinbase Index (Fixed Supply) - a modified version of Coinbase Index which is adjusted to remove the effect of supply increases, so that it can be tracked by investors. For more information, see Section 6 of the Methodology and Construction. So if you invest in this, you're basically making a bet that 'the flippening' will not occur because you would lose bigly relative to the market if bitcoin tanked since they don't rebalance for a year (which is forever in crypto).