Explain whether each of the following events would cause a movement along or a shift in the position of the AD curve, other things being equal. In each case, explain the direction of the movement along the curve or shift in its position.
a. Deflation has occurred during the past year.
b. Real GDP levels of all the nation's major trading partners have declined.
c. There has been a decline in the foreign exchange value of the nation's currency.
d. The price level has increased this year.