We can abstractly understand the trading system as:

Each expected return = Winning rate × Profit per trade – Losing rate × Loss per trade, simplified as: the average of the money earned minus the money lost each time.

Here we introduce three roles:

1. Retail investor: Winning rate 45%, expected return = 0.45 × 1.5 – 0.55 × 1 = +0.125

2. Ordinary trader: Winning rate 50%, expected return = 0.50 × 1.5 – 0.50 × 1 = +0.25

3. Professional trader: Winning rate 55%, expected return = 0.55 × 1.5 – 0.45 × 1 = +0.375

You can see that from retail investors to ordinary traders, a 5% increase in winning rate doubles the return, and a 10% increase raises the expected value by 200%, the gap is much larger than imagined...