Use of "the".

Is the use of “the” in the sentences below correct? :

Oil prices have an effect on the domestic GDP (Gross Domestic Product).

Oil prices have an effect on the domestic CPI (Consumer Price Index).

Oil prices have an effect on the domestic exchange rate.



I felt that since a country has only one GDP, CPI and the exchange rate that “the” should there, but I am not sure.

What about this:

Oil prices have an effect on the value of the domestic currency.

Are both uses of “the” correct?

The definite article is really confusing for me...

Thanks in advance.