Chaikin classifies all US-listed ETFs according a 3-level hierarchy: ETF Category/ ETF Group/ETF Subgroup.
- ETF Category is based on the primary type of asset held by the ETF.
- ETF Group is the primary comparison group of the ETF.
- ETF Subgroup is a more specific set of similar ETFs within the ETF Group.
Although many ETFs have multiple characteristics (e.g. Inverse and Leveraged), rules are applied to assign all ETFs are assigned to only one Category and ETF Group. Most, but not all, ETFs are in a Subgroup.