Overconfidence

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:

1. Stock-picking confidence: 80% retail investors believe they outperform market. Reality: 80% UNDERperform.
2. Trading frequency: overconfident investors trade more, fees + slippage eten alpha
3. Position sizing: overconfident → te concentrated positions → big losses
4. 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:

1. Acknowledge base rates: 'meeste actieve investors underperform — ben ik echt anders?'
2. Track record: keep score van je predictions, see hit rate
3. Index funds: hopeloos pragmatisch en accepting dat je geen edge hebt
4. Pre-mortem: 'wat ALS ik fout zit?'
5. 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.