Goods that are luxuries rather than necessities are 'elastic,' or flexible. That means there is a significant change in the quantity demanded if the price rises or falls. The State of New York has decided to tax sugary sodas, for example. For the tax to be effective, demand for the product would have to be 'elastic,' that is, when the price goes up because of the tax people will buy other drinks instead. If people are addicted to a product, like cigarettes, then a tax is not likely to discourage consumption.