There are many examples of machine learning algorithms later found to be unfair, including Amazon and its recruiting and Google's image labeling. Researchers have been aware of these problems and have worked to impose restrictions that ensure fairness from the outset. For example, an algorithm called CB (color blind) imposes the restriction that any discriminating variables, such as race or gender, should not be used in predicting the outcomes. Another, called DP (demographic parity), ensures that groups are proportionally fair. In other words, the proportion of the group receiving a positive outcome is equal or fair across both the discriminating and nondiscriminating groups.