Demand curves have a negative slope because-
1
Firms tend to produce less of a good that is more costly to produce.
2
The substitution effect always leads consumers to substitute higher quality goods for lower quality goods.
3
The substitution effect always causes consumers try to substitute away from the consumption of a commodity when the commodity's price rises.
4
An increase in price reduces real income and the income effect always causes consumers to reduce consumption of a commodity when income falls.
5
Question Not Attempted