The observable relationship
A BIST index measures a basket of shares in its stated currency. It does not automatically describe your return in dollars, pounds or euros. Currency conversion, dividends, fees and taxes change the result.
A simple illustration
If a share rises 30% in lira while the number of lira per dollar rises 25%, the approximate dollar price return is 1.30 ÷ 1.25 − 1 = 4%, before dividends and costs. These numbers are hypothetical, not a forecast.
What to watch
Compare the same start and end dates, distinguish price from total return, and use actual conversion costs. A stronger local index and a weak home-currency return can occur together.
The deeper question
Which parts of the business earn foreign currency, and which costs or debts are linked to it? The pack develops a full currency and company-risk framework.