Math of portfolio construction -
Which one is a better bet?
Bet A- Flip a coin, heads you win 15 Rs, tails you lose 5 Rs
Bet B- Roll a dice, if it shows 6 you win 15 Rs, if not you lose 3 Rs
Expected value-
Bet A: 50%*15 - 50%*5 = 5 Rs
Bet B: 17%*15 - 83%*3 = 0 Rs
What mattered here was the base rates. In Bet A one wins 50% of the times, in Bet B one wins 1/6th of the times.
Now take this to actual businesses: Higher the return, higher the risk and higher risk means violent downside when you're wrong. So its hard to size a very high upside, high downside bet at 10% of your PF in my view. 40% downside would cost 4% of PF. So generally these high growth bets sit at lower sizing (say ~2%). To achieve same net gain as a 15% compounder, this bet needs to deliver 53% return cagr (and good luck if you're betting on many such 2% bets going right at the same time).
Base rates? Roughly half the stocks (with Mcap > 1000 Cr) have delivered 15% cagr over 3 year period. Only about 12.5% of the same universe have delivered over 53% cagr over 3 years.