The economics term 'inferior good' refers to one which has negative income elasticity of demand, i.e. a good for which an individual's demand falls as their income rises.
Of course, which goods are inferior will vary depending on where you are on the scale. Someone may consume more margarine as they become more affluent, but at some point they may switch to butter or an olive-based spread. At this point in the scale, margarine has a negative income elasticity of demand.
Of course, which goods are inferior will vary depending on where you are on the scale. Someone may consume more margarine as they become more affluent, but at some point they may switch to butter or an olive-based spread. At this point in the scale, margarine has a negative income elasticity of demand.