The rate of return that businesses expect on capital projects is a key determinant of investment. Suppose a technological breakthrough causes an increase in the expected return on investment. Investment spending will rise, and aggregate demand will increase at each price level.
When the incomes of foreigners increase, foreigners will purchase more domestic products, causing exports to rise. Because net exports are one component of aggregate demand, this increase in net exports (exports minus imports) leads to an increase in aggregate demand at each price level.
The level of consumer spending depends, in part, on household wealth. As household wealth rises, consumer spending rises at each price level. An increase in consumer spending leads to an increase in aggregate demand.
A decrease in taxes increases households' disposable income. Households will spend more, causing aggregate demand to increase at each price level.