Explanation:
The aggregate demand curve is downward sloping. It implies price levels are falling and the quantity of output will increase as well as the domestic income. The theories that can explain why the aggregate demand curve is downward sloping: the Pigou's wealth effect, the Keynes's interest-rate effect, and the and Mundell-Fleming's exchange-rate effect.
The Pre-Columbian era incorporates all period subdivisions in the history and prehistory of the Americas before the appearance of significant European influences on the American continent, spanning the time of the original settlement in the Upper Paleolithic period to European colonization during the Early Modern period.
While the phrase "pre-Columbian era" literally refers only to the time preceding Christopher Columbus's voyages of 1492, in practice the phrase is usually used to denote the entire history of indigenous Americas cultures until those cultures were exterminated, diminished, or extensively altered by Europeans, even if this happened decades or centuries after Columbus's first landing. For this reason the alternative terms of Precontact Americas, Pre-Colonial Americas or Prehistoric Americas are also in use. In areas of Latin America the term usually used is Pre-Hispanic.
