Giffen goods
For most products, price elasticity of demand is negative. In other words, price and demand pull in opposite directions; price goes up and demand goes down, or vice versa. Giffen goods are an exception to this. Their price elasticity of demand is positive. When price goes up demand also goes up, and vice versa. In order to be a true giffen good, price must be the only thing that changes to get a change in demand.
Despite years of searching, no generally agreed upon example has been found. Some types of premium goods (such as expensive French wines, or celebrity endorsed perfumes) are claimed to be giffen goods. It is claimed that lowering the price of these high status goods can decrease demand because they are no longer perceived as exclusive or high status products. However, since the actual good is 'high status' and not the wine (, perfume ...) the price of the 'high status' has not gotten cheaper, so goods like this are not usually considered giffen goods.
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