SavvyGrowthPaths

Most investors believe investing success comes from finding great stocks.

In reality, wealth is often determined by something more subtle:

How much capital you allocate when you are right.

The Kelly Criterion provides a rational framework to decide the optimal size of an investment when you believe you have an edge.

Its purpose is simple:

Maximise long-term compounding while avoiding ruin.

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The Kelly Formula

The basic Kelly formula is:

f* = (bp − q) / b

Where:

• f* = fraction of total portfolio to invest
• p = probability of success
• q = probability of failure (1 − p)
• b = payoff ratio (gain relative to amount invested)

This formula converts investment conviction into a disciplined position size.

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A Clear Investing Example

Suppose you analyse a stock trading significantly below intrinsic value.

After careful analysis you estimate:

• Probability stock succeeds = 60%
• Expected upside = 50%
• Possible downside = 25%

Here the payoff ratio b = 0.50 / 0.25 = 2

Applying Kelly:

f* = (2 × 0.60 − 0.40) / 2
f* = (1.20 − 0.40) / 2
f* = 0.40

Kelly suggests investing 40% of your portfolio in this opportunity.

This does not mean you must invest 40%.
Many disciplined investors use Half-Kelly → 20% allocation
to reduce volatility and emotional pressure.

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The Powerful Insight

Kelly naturally creates intelligent concentration.

• Weak ideas → small or zero allocation
• Average ideas → moderate allocation
• Exceptional ideas → meaningful capital commitment

This is very different from mechanical diversification.

True diversification is not about owning many stocks.
It is about sizing each position according to expected edge.

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Why This Matters for Long-Term Wealth

Even if you identify undervalued stocks correctly:

• Investing too little reduces the impact of correct decisions
• Investing too much increases the probability of permanent loss

Kelly sits precisely between fear and overconfidence.

It transforms investing from opinion into probability-weighted capital allocation.

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Final Thought

Investing success is not only about being right.

It is about being right in the right size.

In the long run, portfolios are shaped less by ideas
and more by the intensity with which capital backs those ideas.

Happy Investing!