What is gain percentage?

What it means

A raw balance change is meaningless on an account that has been topped up: deposit $5,000 into a $5,000 account and the balance doubles without a single trade. Gain corrects for this by measuring only the part attributable to trading, typically by chaining the returns of each period between cash movements.

Why it matters

The correction introduces its own distortion. Because the periods are compounded, a large gain earned while the account was small keeps its full weight forever, even after the account grows tenfold and never repeats it. An account showing 400% gain may have made almost all of it in one early month on a few hundred dollars — the figure is not wrong, it simply is not what a new subscriber will experience.

What this changes in practice

The reliable reading is to ignore the headline and open the monthly table. Twelve mediocre positive months are a system; one enormous month and eleven flat ones are an event. Cross-check against maximum drawdown and deposit load, because a high gain produced at high risk is a description of the risk, not of the skill.