The suggestion is that we would be able to say that one allocation is better than another if at least one person is better off under the first allocation and no-one is worse off. This is called the Pareto criterion. If we change from one allocation of resources to another, for example if it were possible to make changes to the health care system in terms of the kind of care that is made available, and this means that some people benefit and no-one is made worse off, then this is described as a Pareto improvement.