The law of demand states that as long as other factors (like income, taste, price of related goods/services, etc.) remain the same there is an inverse relationship between price and demand. The higher the price, the lower the demand. Conversely lower prices will result in higher demand.
The chart below shows the relationship between price (on the vertical axis) and demand (on the horizontal axis).
Exceptions & Limitations
There are cases in which demand does not inversely relate to price as predicted by the law of demand...
Basic or Essential Goods
Increasing the price of things like medicine or fuel does little to decrease demand, at least in the short term. Likewise a decrease in price does not generate increased demand.
Veblen Good
Some products contradict the law of demand – higher prices actually increase demand. One such group of products are known as Veblen goods. The demand for some luxury goods like premium wines & spirits, purses and handbags, watches & jewelry, and high performance/exotic automobiles is based on their high price, which sends a powerful message about their quality, status and exclusivity. Decreasing prices would (contrary to the law of demand) decrease demand because the goods would no longer be perceived the same way.
New Alternatives/Substitute Products
The arrival of alternatives or substitutes may lower demand regardless of the price of the original product. An example would be tablets, which reduced demand for traditional computing devices even as those prices remained constant (and sometimes even reduced). This is also seen in entertainment media where digital downloads replaced the CDs that replaced the cassettes that replaced eight-track cassettes, regardless of the price difference.
Changes in Taste
Most pronounced in fashion – one year everyone has to have Ugg boots or the Canada Goose jacket, and a year or two later something else becomes the rage. This kind of change in demand does not correspond with change in price but rather a change in taste.
Anticipated Change in Price and/or Availability
Demand may increase when prices are expected to rise and/or shortages are anticipated. For example the forecast of an early snow will often lead to increased short term demand for ice salt, snow shovels and snow tires. Demand may also decrease when prices are expected to fall.
Related Products
Demand for one product may be reduced by a rise in the cost of related products. For example an increase in airfares may decrease the demand for hotel rooms. An increase in fuel prices may reduce the demand for less fuel efficient vehicles and increase the demand for hybrids.