Which products, if any, will have a perfectly inelastic demand?

When a product has a relatively inelastic demand, a 10% rise in price would cause a decline in quantity demanded that is smaller in absolute value: for example, 8%. If the demand for a product were perfectly inelastic, a rise in price would have no effect on demand at all. For example, a 10% rise in price would cause a 0% decline in quantity. The demand curve for the product would be completely vertical.

Here are some products that have relatively inelastic demand:

a)	gasoline (Think about the short run; ask yourself how consumers would respond to a price change in the first month),
b)	heroin,
c)	insulin, and
d)	light bulbs.

Pick one of the products. How, if at all, could consumers adjust to a rise in the product's price? Decide whether you think the product has perfectly inelastic demand. To say it another way, decide whether you think the demand curve will be vertical, or just quite steep?

As you answer the question, remember that more substitutes for a product make the demand more elastic. Think about what might substitute for the product you pick. Be creative, realize that some substitutes are quite like the product they replace (tea is a hot beverage containing caffeine), but some are not (a letter might substitute for a telephone call).