They may cease to exist in a Markowitz model, although rational actors can introduce them in more complicated scenarios. When they are injected into the Slutsky Equation, the result is a uniquely negative semidefinite symmetry. Alfred Marshall devoted approximately ten lines of his Principles of Economics to them originally, and Uriel Spingel argued that public transportation was one. They clearly differ from the Veblen type, which factor in conspicuous consumption, and two Harvard economists have made the case for rice and noodles being ones in parts of China. FTP, name these theoretical inferior goods most famously 
They may cease to exist in a Markowitz model, although rational actors can introduce them in more complicated scenarios. When they are injected into the Slutsky Equation, the result is a uniquely negative semidefinite symmetry. Alfred Marshall devoted approximately ten lines of his Principles of Economics to them originally, and Uriel Spingel argued that public transportation was one. They clearly differ from the Veblen type, which factor in conspicuous consumption, and two Harvard economists have made the case for rice and noodles being ones in parts of China. FTP, name these theoretical inferior goods most famously exemplified by potatoes during the Irish potato famine.
They may cease to exist in a Markowitz model, although rational actors can introduce them in more complicated scenarios.
Giffen good (prompt inferior goods)