When Does CAPM Fail? Limitations Explained

After Risk vs Return astatine the Portfolio Level, the earthy question and reply mobility is whether a azygous market-risk measurement is capable to value expected return. The Capital Asset Pricing Model (CAPM) is the workhorse of finance theory, but practitioners cognize it breaks down successful galore real-world situations. Understanding these failures differentiates blase candidates.

• CAPM: E(R) = Rf + β × (Rm − Rf) wherever β = systematic consequence comparative to market.
• CAPM breaks down because azygous clip play assumptions meet multi-period, changing risk, truthful beta is not unchangeable complete time.
• CAPM assumes β captures each risk, but aggregate consequence factors matter, and Fama-French explains better.
• In India, taxes and transaction costs matter: STT 0.1%, STCG 20%, LTCG 12.5%, truthful taxation resistance changes optimal holding.
• Indian marketplace beta for large-cap IT stocks specified arsenic Infosys and TCS vs Nifty 50 averages ~0.7-0.8 complete 5 years but tin plaything from 0.5 to 1.2 during different marketplace cycles.
• In India, usage CAPM only arsenic a starting constituent and set for size premium, illiquidity premium, and state consequence premium.

Big Picture

CAPM is useful because it gives a cleanable starting discount-rate model, but its assumptions often do not lucifer existent marketplace conditions. The cardinal failures travel from unstable beta, behavioural mispricing, accusation asymmetry, aggregate consequence factors, concentrated portfolios, and real-world frictions for illustration taxes and transaction costs.

CAPM: E(R) = Rf + β × (Rm − Rf) wherever β = systematic consequence comparative to market.

CAPM Assumptions Versus Reality

Indian marketplace beta for large-cap IT stocks (Infosys, TCS) vs Nifty 50 averages ~0.7-0.8 complete 5 years but tin plaything from 0.5 to 1.2 during different marketplace cycles. Key factors: (1) Global macro sensitivity (USD/INR for IT); (2) Sector rotation; (3) FII flows (FIIs clasp ~20% of NSE free float; their exits create non-linear beta spikes). So CAPM should beryllium utilized only arsenic a starting point, not arsenic the last discount rate.

Portfolio Implication

In India, usage CAPM only arsenic a starting point. Adjust for the pursuing premiums to get a much realistic discount complaint than axenic CAPM.

Fama-French 3-Factor Model

Fama-French (1993) showed that a 3-factor exemplary explains banal returns acold amended than CAPM:

E(R) = Rf + β₁(Market Premium) + β₂(SMB) + β₃(HML)

Where: SMB = Small Minus Big (small-cap premium); HML = High Minus Low (value premium - precocious B/P outperforms). In India, SMB premium has been substantial: Nifty Smallcap 250 delivered ~20% CAGR vs Nifty 50's ~14% complete 2014-2024, accordant pinch Fama-French predictions.

Why Beta Becomes Unstable successful Emerging Markets

Beta instability is 1 of the clearest ways CAPM fails successful emerging markets. Indian marketplace beta for large-cap IT stocks (Infosys, TCS) vs Nifty 50 averages ~0.7-0.8 complete 5 years but tin plaything from 0.5 to 1.2 during different marketplace cycles.

Key factors: (1) Global macro sensitivity (USD/INR for IT); (2) Sector rotation; (3) FII flows (FIIs clasp ~20% of NSE free float; their exits create non-linear beta spikes).

Structuring a When Does CAPM Fail? Limitations Explained Interview Answer

"What are CAPM's limitations?"

The strongest reply does not cull CAPM completely. It says CAPM is simply a floor, past adds size and liquidity premiums for emerging marketplace application.

The astir predominant correction is treating CAPM arsenic a complete real-world discount-rate model. That costs points because it ignores beta instability, aggregate consequence factors, taxes, transaction costs, concentration, and liquidity premiums.

Conclusion

CAPM remains a useful starting point, but it fails erstwhile marketplace assumptions do not lucifer reality. For emerging marketplace application, the amended question and reply answer is to usage CAPM arsenic a level and set for size, liquidity, and state consequence premiums.