Technological development enables human societies to expand the whole Pareto Optimal curve. This means we can reach better fairness without many people forced to be worse off . (Amir, 20Aug2013)

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A Weak Pareto efficiency is the result of a change that makes at least one party better off, and does not make any party worse off. In curve below a Move from B to C, A to B, A to D,  causes a weak Pareto efficiency.

The strong Pareto efficiency is the result of a change in allocation in which all dimensions gain. In curve below a Move from A to C, or from A to any point on CD causes a strong Pareto efficiency.

A a Pareto inefficiency is an allocation in which we can find at least a weak Pareto efficient reallocation.

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A Weak Pareto Optimality, is an allocation in which, all resources have been exhausted and, we can not find a change that benefits all dimensions. Any change will make at least one party unchanged. In the curve below, for A, BC is Weak Pareto Optimal and  CD is strong Pareto optimal.

A Strong Pareto Optimality, is an allocation in which, all resources have been exhausted and, we can not find a change that benefits all dimensions. Any change will make at least one party worse off