Final answer:
The "F" in the model GDP = C + I + G + F stands for net exports, which is the difference between a country's exports and imports, also known as the trade balance.
Step-by-step explanation:
In the model GDP = C + I + G + F, the "F" represents the net exports component of a country's Gross Domestic Product (GDP). More precisely, F stands for the dollar value of exports (X) minus the dollar value of imports (M), which is expressed as (X - M). This difference is known as the trade balance. If a country exports more than it imports, it has a trade surplus; if it imports more than it exports, there is a trade deficit. For example, in the United States during the 1960s and 1970s, exports typically exceeded imports, signalling a trade surplus. However, since the early 1980s, the situation has reversed, with imports surpassing exports, indicating a trade deficit.