These decisions added a legal dimension to trade-offs between "efficiency and equity" referenced by Murphy. Though cognitive testing is generally inexpensive, reliable and valid, US employers risk expensive legal action if such testing produces disparate impact. In practice, companies have responded with a variety of strategies, from abandonment of cognitive testing to maintenance of racial hiring quotas. The latter derives from enforcement of the Equal Employment Opportunity Commission's "four-fifths rule", which states that any group selection rate that is less than four-fifths (80%) of the highest rate will be regarded by Federal enforcement agencies as evidence of adverse impact.