I tried to do it based on a Mathematical Model:
Clearly, there’s no single formula that I can give you. It differs from person to person. But consider these sub-components
- Expected loss in Value / Expected Drawdown if Risks materialize (Lower the loss, higher the allocation)
- Probability of Risks materializing (Lower the Probability, higher the allocation)
- Expected Returns if Risks don’t materialize (Lower the Returns, lower the allocation)
Some combination / weight to these points based on your personal experiences / opinions should determine the allocation to each stock.
Then, as an additional step, you can have thumb rules. Ex: Not more than 10% in BFSI, not more than 20% in a single stock / sector and so on. By definition, there’s no defined logic behind thumb rules. They’re mostly safety measures.