The Risks of the Rise of Passive Investing | Mike Green

In this episode of Excess Returns, Mike Green returns to dissect the structural transformation underway in public markets due to the rise of passive investing. He explains why “there’s no such thing as a passive investor,” how inelastic flows distort prices, and what it means for valuation, volatility, and the long-term sustainability of equity markets. From the math behind market multipliers to the policy distortions driving mega-cap dominance, Mike walks through the macro, micro, and behavioral implications of passive flows — and what investors and policymakers need to do about it. 🔍 Topics Covered: Why passive investing isn’t truly passive The origins and impact of the inelastic market hypothesis How passive flows distort price discovery The shift from mean reversion to mean expansion in markets Multipliers and the mechanics of how flows drive prices Why market efficiency is breaking down at scale The hidden risks of passive-dominant market structure Target date funds and their unintended consequences The fragility of valuations under passive dominance The problem with IPO scarcity and capital misallocation Options strategies for convex tails and market drift Why the Fed and regulators may act — and what could trigger it Bitcoin and private markets as new flow-driven regimes How policy and tax advantages have reshaped capitalism ⏱️ Timestamps: 00:00 – "There’s no such thing as a passive investor" 01:05 – The origins of Mike’s work on passive flows 03:00 – Bill Sharpe vs. Lasse Pedersen on passive flaws 06:00 – Index rebalancing and the illusion of passivity 07:00 – The rise of flow-based (demand-side) asset pricing 10:00 – Why EMH broke down under scale 12:00 – The human layer markets forgot 14:30 – The math behind price multipliers (5x to 25x) 17:00 – Market efficiency vs. market distortion 20:00 – Meta, index drift, and fake efficiency 23:00 – What individual investors should do 25:00 – The Mag 7 and extreme multiplier effects 27:00 – Options and convex tail risk management 29:00 – Mike’s 2016 survey on marginal buying behavior 31:00 – The shift from mean reversion to mean expansion 33:30 – When the music stops: wealth-to-income dynamics 35:00 – Theoretical crash under net withdrawals 36:00 – Why the boomer selloff thesis is flawed 39:00 – The overlooked risk: wealthy investors exiting actives 41:00 – Public vs. private equity concentration 43:00 – Why policy response is likely (and how it may look) 46:00 – Political power vs. market dominance 49:00 – Bitcoin, passive ETFs, and flow-driven pricing 52:00 – Private equity in 401(k)s — implications and risks 57:00 – The unintended outcomes of inflated valuations 59:00 – The hollowing out of the public equity bid 1:01:00 – How Vanguard’s 2015 rebalancing moved the market 1:04:00 – Valuation opacity and future withdrawals 1:07:00 – What Mike is working on now and next steps