Final answer:
The United States went off the gold exchange standard in 1971 primarily because it wanted more control over its monetary policy.
Step-by-step explanation:
The reason behind the United States going off the gold exchange standard in 1971 was primarily because the United States wanted to have more control over its monetary policy.
By allowing the dollar to flow freely against the price of gold, it caused a devaluation of the dollar, which made American goods cheaper abroad and stimulated exports, ultimately addressing the balance-of-payments deficit. This move marked the beginning of the end of the dollar's dominance in international trade.