4 Research Papers You Should Read | In the Money by Zerodha

ELI5/TLDR

Sepra walks through four foundational research papers that rewrote how we think about markets. Start with Markowitz’s 1952 insight that risk is measurable and diversification is free lunch. Jump to Sharpe’s CAPM which says only systematic risk (the kind you can’t diversify away) matters for returns. Then Fama admits his own efficient market theory has cracks, yet engineers a philosophical escape hatch. Finally, Fama and French demolish CAPM by showing company size and cheapness explain returns far better than risk ever did. Seventy years of finance compressed into one episode.

The Full Story

Research Papers vs Books

Before diving in, Sepra clarifies what makes a research paper different from a business book. A book sells a narrative; a paper answers a specific question through methodology, data, and peer review. Most papers fail peer review. The ones that survive, especially those cited thousands of times, become foundational because experts in the field kept building on them. This is why academic research, despite its ivory-tower reputation, tends to outlast practitioner heuristics.

Markowitz: The Birth of Portfolio Theory (1952)

“It is necessary to avoid investing in securities with high covariances among themselves.”

Before Markowitz, conventional wisdom was simple: find the best stock, put all your money there. Markowitz reframed investing as a science. Risk, he showed, is measurable—it’s the variance of your returns. The radical insight: two risky stocks can reduce each other’s risk if they don’t move together. This gave us the efficient frontier (for any level of risk, there’s an optimal portfolio) and what Sepra calls the only free lunch in investing: diversification. Markowitz won the Nobel Prize 38 years after publishing.

Sharpe: Pricing Risk with Beta (1964)

Sharpe built on Markowitz and answered the next question: why do some assets give higher returns? His answer: they carry more systematic risk—the kind of risk you cannot diversify away. If a single stock tanks, that’s avoidable risk (you should have diversified). But when the market crashes, everything falls. There’s no portfolio construction that saves you. So the market compensates you for bearing that unavoidable systematic risk. This compensation is your excess return. Beta quantifies how much systematic risk a stock carries (beta of 2 means twice as volatile as the market). CAPM follows: Expected Return = Risk-Free Rate + Beta × Market Risk Premium. Elegant, simple, and incomplete—which later papers would prove.

Fama: Efficiency Under Scrutiny (1991)

Twenty-one years after his original efficient market hypothesis paper, Fama returns with Part Two. The core idea stands: security prices fully reflect all available information. But the evidence? It’s messy. Returns are somewhat predictable from past returns, dividend yields, and interest rate spreads. For a strong efficiency believer, this is awkward. Fama’s response: just because returns are predictable doesn’t mean markets are inefficient. To prove inefficiency, you’d need a perfect model of what “correct” returns should be. Since all models are imperfect, how do you know if the market is wrong or your model is? He calls this the joint hypothesis problem. Critics call it a convenient escape hatch.

Shiller’s counterargument hits harder: stock prices are far more volatile than their dividends. A company paying steady dividends should have a stable stock price. It doesn’t. That volatility looks like crowd behavior, not rational risk assessment. This debate was so central to finance that Fama and Shiller shared the 2013 Nobel—arguably the most awkward joint Nobel in history, given they fundamentally disagree on whether markets are efficient.

Fama-French: Beta Is Dead (1992)

The killing blow comes a year later. Fama and French run data from 1963-1990 and find that beta—the centerpiece of CAPM—has almost no explanatory power for stock returns. What actually explains returns? Company size and valuation (price-to-book). Small companies outperform large ones. Cheap companies outperform expensive ones. This paper births factor investing and opens a question that remains unsettled: Are size and value premiums compensation for real risk, or is the market simply mispricing these stocks? Fama leans toward risk; behavioral economists like Shiller lean toward mispricing.

Key Takeaways

Markowitz (1952): Risk is variance. Diversification across uncorrelated assets reduces risk without reducing return—the only free lunch in investing.
Sharpe (1964): Only systematic risk (market risk you cannot diversify) deserves compensation. Beta measures it. CAPM prices that risk.
Fama (1991): Markets are hard to beat. Returns are somewhat predictable, but Fama dodges the inefficiency charge via the joint hypothesis problem. Shiller says the volatility mismatch proves irrational behavior.
Fama-French (1992): Size and value factors explain returns; beta does not. Shifts the conversation from CAPM to multifactor models. Leaves unresolved whether these premiums are risk or mispricing.

Claude’s Take

This is a strong foundational distillation. Sepra’s framing—academic ideas eventually become the frameworks practitioners operate within, often without realizing it—is the real insight. The papers themselves are canonical and well-explained. What stands out is the narrative of theory being built, stress-tested, and partially demolished by the same people who built it. Fama’s retreat into the joint hypothesis problem is particularly interesting because it’s a philosophical boundary rather than empirical; it makes efficiency unfalsifiable, which is why critics call it an escape hatch. The size and value factors matter because they’re still debated (risk vs mispricing), which means there’s still money in the question. A solid synthesis for anyone who wants to understand why the research papers in finance matter more than most trading books.

Score: 7/10. Clear synthesis of canonical material, well-structured narrative, but not breaking new ground. The value is in seeing the tensions—Sharpe vs Fama-French, Fama vs Shiller—as a coherent intellectual history. Worth understanding before you build any investment thesis.