 Implementing first-best principles can have important secondary consequences. To take one example, the scheme the U.S. introduced in 1989 to allocate kidneys increased the weighting for immune system compatibility and the effect was to reduce the proportion of African-Americans transplanted (Elster 1992: ch. 5). Many thought the result inequitable because of the disparate impact even though the difference was not due to overt discrimination (see the entry on  justice, inequality, and health).