Final answer:
Since 1999, the purchasing power of the U.S. dollar has increased relative to the purchasing power of Canada, as evidenced by the fluctuating exchange rates between the two currencies over the years.
Step-by-step explanation:
The changes in the purchasing power of the U.S. dollar relative to other currencies. The exchange rates between the U.S. dollar and other currencies like the Canadian dollar have fluctuated substantially over the years. A comparison of the exchange rate trends and purchasing power between the U.S. dollar and the Canadian dollar shows that from 1980 to August 2022, the U.S. dollar has seen periods of appreciation (or strengthening) and depreciation (or weakening) against the Canadian dollar.
For instance, the U.S. dollar appreciated from $1.17 Canadian in 1980 to $1.60 Canadian by early 2002. It later depreciated to roughly $1.20 Canadian in 2009. As of August 2022, the U.S. dollar stood at $1.28 Canadian. Given this data and considering the options provided, the correct answer would be that since 1999, the purchasing power of the U.S. dollar has increased relative to the purchasing power of Canada.