pareto condition

"Pareto efficiency, or Pareto optimality, is an important notion in neoclassical economics with broad applications in game theory, engineering and the social sciences. Given a set of alternative allocations and a set of individuals, a movement from one allocation to another that can make at least one individual better off, without making any other individual worse off, is called a Pareto improvement or Pareto optimization. An allocation of resources is Pareto efficient or Pareto optimal when no further Pareto improvements can be made."

In other words, you can do nothing for a better economic efficiency when Pareto optimization is achieved.

"If an economic system is Pareto efficient, then it is the case that no individual can be made better off without another being made worse off. It is commonly accepted that outcomes that are not Pareto efficient are to be avoided, and therefore Pareto efficiency is an important criterion for evaluating economic systems and political policies.

If economic allocation in any system (in the real world or in a model) is not Pareto efficient, there is theoretical potential for a Pareto improvement - an increase in Pareto efficiency: through reallocation, improvements to at least one participant's well-being can be made without reducing any other participant's well-being.

In the real world ensuring that nobody is disadvantaged by a change aimed at improving economic efficiency may require compensation of one or more parties. For instance, if a change in economic policy dictates that a legally protected monopoly ceases to exist and that market subsequently becomes competitive and more efficient, the monopolist will be made worse off. However, the loss to the monopolist will be more than offset by the gain in efficiency. This means the monopolist can be compensated for its loss whilst still leaving an efficiency gain to be realised by others in the economy. Thus, the requirement of nobody being made worse off for a gain to others is met."

For more details, please refer to wikipedia

There is Chinese version in wikipedia but maybe even more difficult to understand.

pareto condition:
its impossible to rearrange resources to gains without hurting others
OR its impossible to reallocate resources to gain with compensating others
OR its impossible to make everyone gain
即係去到pareto condition呢個位，
社會唔可以再調動資源去賺取利益, 否則有人會損失..
或者有人損失左，社會賠償返比佢，稔住overall既gain會cover到賠償，但去到pareto condition唔得，賠左都無得再賺返。
因為有constraint既關係(e.g. transaction cost)，人只可以係有限條件爭取最大利益，為之constraint maximization，所以考慮晒所有因素，一個決定可以令人gain得最多，就叫pareto condition! 呢個決定/資源既調動已經係最好，已經係最有效益，efficiency因此已經attain到。