Overconfidence
Onderschatten risico, overschatten eigen skill.
Overconfidence is een van de meest documented behavioral biases. Mensen ZIEN zichzelf als beter dan gemiddeld — vooral bij complexe taken.
Famous statistics:
- 80% van automobilisten denkt 'beter dan gemiddeld' (mathematically impossible — only 50% kan beter dan median)
- 90% van entrepreneurs verwacht success, terwijl historical base rate ~10% is
In beleggen:
- Stock-picking confidence: 80% retail investors believe they outperform market. Reality: 80% UNDERperform.
- Trading frequency: overconfident investors trade more, fees + slippage eten alpha
- Position sizing: overconfident → te concentrated positions → big losses
- Ignoring contrary evidence: 'I know better than analysts'
Gender differences:
Barber & Odean (2001) studie: men more overconfident dan women → trade more → lower returns. Women statistically better investors door minder trading.
Antidote:
- Acknowledge base rates: 'meeste actieve investors underperform — ben ik echt anders?'
- Track record: keep score van je predictions, see hit rate
- Index funds: hopeloos pragmatisch en accepting dat je geen edge hebt
- Pre-mortem: 'wat ALS ik fout zit?'
- Munger's mental models: gebruik invalidating evidence
Buffett:
'I don't try to jump over 7-foot bars. I look around for 1-foot bars that I can step over.' Accept your level, don't overreach.