Module XIX·Article I·~2 min read

Loss Aversion

Investor Psychology and Behavioral Finance

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Loss Aversion: asymmetry in the perception of gains and losses

Loss Aversion (loss aversion) is a fundamental cognitive bias discovered by Daniel Kahneman and Amos Tversky. People experience the pain of loss about twice as strongly as the joy from an equivalent gain.

Kahneman–Tversky Experiment

Choice between:

A: Guaranteed to receive $50
B: 50% chance to receive $100, 50% chance to receive $0

Mathematically: EV(A) = EV(B) = $50.
But most people choose A.

Now the choice between:

C: Guaranteed to lose $50
D: 50% chance to lose $100, 50% chance to lose $0

Most people choose D (risk) to avoid a guaranteed loss!

Loss aversion coefficient $\lambda \approx 2.0$–$2.5$

Losing $100 feels like losing $200\text{–}250$ in terms of utility.

Consequences for Investors

BehaviorDescriptionResult
Disposition EffectSell winners too early, hold losers too long"Locking in profits" but not losses
Panic SellingSell during crisis at the lowsRealize losses, miss recovery
Risk Aversion increases after lossesBecome too conservativeMiss out on recovery
Over-tradingDesire to "win back losses"Transaction costs, worse timing

Disposition Effect: Data

Study by Terrance Odean (UC Berkeley):

  • Investors sell winning positions 50% more often than losing ones
  • At the same time, sold winners continue to rise
  • Held-on losers continue to fall

Result: -3.4% annual underperformance

Market-wide effects

PhenomenonMechanism
MomentumWinners sold too early → underreaction
CrashesPanic selling → cascade → overshooting
Recovery speedFear keeps investors out → slow recovery participation

Defensive mechanisms for CIO

MechanismDescriptionEffectiveness
Pre-commitmentSale rules in IPS before eventsHigh
Investment CommitteeCollective decision-makingHigh
Automatic RebalancingRules-based, removes emotionHigh
Cooling-off periods24-48 hours before major decisionsMedium
Devil's AdvocateSomeone always argues againstMedium

Reframing: changing perspective

Loss Aversion FramingRational Reframing
"I lost $50,000""Portfolio dropped by 5% — this is normal volatility"
"I need to sell to stop the pain""Selling at the bottom — worst possible timing"
"The market will never recover""Historically markets have always recovered"

Pre-mortem analysis

Before investing, imagine that it failed. Why?
Document potential reasons for failure
Define in advance when you will sell
Coordinate with committee before the emotional moment

CIO Recommendations

  • Know thyself — admit that you are subject to this bias
  • Rules-based approach — IPS with clear rules
  • Avoid checking portfolio daily — less noise = fewer emotions
  • Long-term framing — think in years, not days
  • Stress inoculation — discuss crisis scenarios in advance

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