Harberger's Triangle, widely used in welfare economics, is named after him.

The efficiency loss is depicted on the demand curve and supply curve diagrams as the area inside Harberger's Triangle.

Harberger's triangle, generally attributed to Arnold Harberger, refers to the deadweight loss (as measured on a supply and demand graph) associated with government intervention in a perfect market.

A subtler critique is a point Richard Posner raised in 1975, namely that the welfare cost of monopoly should include all monopoly profits as well as Harberger's triangle.