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Ep. 3: Modigliani & Miller · 1958 — Capital Structure Irrelevance
In 1958, two young economists published a paper that enraged corporate finance professors and quietly rewired the foundations of the field. Franco Modigliani and Merton Miller’s “The Cost of Capital, Corporation Finance and the Theory of Investment” claimed that, in a perfect market, a firm’s value is completely independent of how it mixes debt and equity—an idea so radical that many dismissed it as academic trickery.
In this third episode of Finance Papers, we strip away the folklore and walk through Modigliani & Miller’s original text section‑by‑section. Instead of treating “capital structure irrelevance” as a slogan, we focus on the arbitrage proof itself: the intellectual “magic trick” where investors reshuffle equity and debt between identical firms to expose any supposed free lunch.
Key Topics Covered in This Deep Dive:
The Irrelevance Benchmark: Why, under no taxes, no distress costs, no agency problems and symmetric information, leverage alone cannot change firm value—only redistribute risk and cash flows across claimholders.
Homemade Leverage: How investors can lever or de‑lever their own portfolios using borrowing and risk‑free assets, and why this undermines the idea that managers can create value purely by changing the debt‑equity mix.
The Arbitrage Argument: Step‑by‑step through MM’s invariance proof, showing how any mispricing between levered and unlevered firms translates into a true free lunch until prices converge.
From Irrelevance to Frictions: How the theorem doesn’t say “capital structure never matters”, but instead tells you exactly where to look when it does—tax shields, bankruptcy and distress costs, agency conflicts, and information asymmetry.
Closing the Foundations: How Modigliani & Miller complete the structural base laid by Markowitz (portfolios) and Sharpe (CAPM), and set the stage for Fama’s formalization of “perfect markets” and the Efficient Market Hypothesis.
Paper Explored: Modigliani, F. & Miller, M. H. (1958), “The Cost of Capital, Corporation Finance and the Theory of Investment”, The American Economic Review, 48(3): 261–297.
🔗 Read the full paper: https://www.jstor.org/stable/1809766
Finance Papers is conceptualized and curated by Luiz Gidrão, CFA, CAIA (founder of stock.cash and goa.capital). Hit play, open the PDF, and learn with us.
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By Luiz Gidrão, CFA, CAIAIn 1958, two young economists published a paper that enraged corporate finance professors and quietly rewired the foundations of the field. Franco Modigliani and Merton Miller’s “The Cost of Capital, Corporation Finance and the Theory of Investment” claimed that, in a perfect market, a firm’s value is completely independent of how it mixes debt and equity—an idea so radical that many dismissed it as academic trickery.
In this third episode of Finance Papers, we strip away the folklore and walk through Modigliani & Miller’s original text section‑by‑section. Instead of treating “capital structure irrelevance” as a slogan, we focus on the arbitrage proof itself: the intellectual “magic trick” where investors reshuffle equity and debt between identical firms to expose any supposed free lunch.
Key Topics Covered in This Deep Dive:
The Irrelevance Benchmark: Why, under no taxes, no distress costs, no agency problems and symmetric information, leverage alone cannot change firm value—only redistribute risk and cash flows across claimholders.
Homemade Leverage: How investors can lever or de‑lever their own portfolios using borrowing and risk‑free assets, and why this undermines the idea that managers can create value purely by changing the debt‑equity mix.
The Arbitrage Argument: Step‑by‑step through MM’s invariance proof, showing how any mispricing between levered and unlevered firms translates into a true free lunch until prices converge.
From Irrelevance to Frictions: How the theorem doesn’t say “capital structure never matters”, but instead tells you exactly where to look when it does—tax shields, bankruptcy and distress costs, agency conflicts, and information asymmetry.
Closing the Foundations: How Modigliani & Miller complete the structural base laid by Markowitz (portfolios) and Sharpe (CAPM), and set the stage for Fama’s formalization of “perfect markets” and the Efficient Market Hypothesis.
Paper Explored: Modigliani, F. & Miller, M. H. (1958), “The Cost of Capital, Corporation Finance and the Theory of Investment”, The American Economic Review, 48(3): 261–297.
🔗 Read the full paper: https://www.jstor.org/stable/1809766
Finance Papers is conceptualized and curated by Luiz Gidrão, CFA, CAIA (founder of stock.cash and goa.capital). Hit play, open the PDF, and learn with us.