Either a decrease in population or a decrease in income will cause consumers to demand goods and services at each price level.
more
less
the same

Either a decrease in population or a decrease in income will cause consumers to demand less goods and services at each price level. This can be seen from the demand curve: which shows how much buyers are willing and able to buy at different prices (he price is plotted on the vertical (Y) axis while the quantity is plotted on the horizontal (X) axis). The demand for a normal product rises when income rises, and vice versa. So, in our case if the goods are "normal" the demand will be decreased