Competing in the marketplace for exchange-traded funds — aka "The Terrordome" — is not for the faint of heart. It's like fighting a multi-front war where issuers have to market existing funds; engage in fee wars with the likes of Vanguard and BlackRock; and innovate in a rapidly changing industry, which now includes more than 300 firms. Only the strong thrive.

On this episode of Trillions, Eric Balchunas and Joel Weber speak with Brian Hartigan, the global head of ETFs and index investments at Invesco. The fourth-biggest ETF issuer in the US, Invesco has about $800 billion in assets under management and saw inflows of $67 billion in 2025. They discuss how the company competes against the industry's "Big Three," the secret behind QQQ's dramatic success and the surprising staying power of smart-beta ETFs. They also explore whether there are simply too many ETFs and how retail investors should assess volatile assets, like Bitcoin.