Determinants of the price elasticity of demand
Consider some determinants of the price elasticity of demand:
1. The availability of close substitutes
2. Whether the good is a necessity or a luxury
3. How broadly you define the market
4. The time horizon being considered
A good with many close substitutes is likely to have relatively demand, since consumers can easily choose to purchase one of the close substitutes if the price of the good rises.
A good’s price elasticity of demand depends in part on how necessary it is relative to other goods. If the following goods are priced approximately the same, which one has the least elastic demand?
A heart valve for heart attack victims
Diamond necklace
The price elasticity of demand for a good also depends on how you define the good.
Organize the goods found in the following table by indicating which is likely to have the most elastic demand, which is likely to have the least elastic demand, and which will have demand that falls in between.
Categories Most Elastic In Between Least Elastic
Red bell peppers
Vegetables
Food
The price elasticity of demand is also affected by the given time horizon.
Other things being equal, the demand for natural gas will tend to be elastic in the short run than in the long run.

If the absolute value of price elasticity is greater than one, it means demand is elastic. Elastic demand means that quantity demanded is sensitive to price changes.

Demand is inelastic if a small change in price has little or no effect on quantity demanded.

a good that is considered a necessity usually has a less elasticity of demand.

the more narrowly defined a good is, the less elastic demand is. for example, there are many substitutes for food because it is largely defined, so its elasticity of demand would be more elastic

in the short run, demand is usually less elastic because there is a short time to find suitable substitutes. but in the long run, consumers have enough time to find suitable substitutes so demand is usually more elastic