Explain the main contribution for Vilfredo Pareto, Economist of neo-classical school of Economic Thought and how his contributions have improved the modern day understanding and application of Economics.
( In 400 words)
He laid the foundation of modern welfare economics with his concept of the so-called Pareto Optimum, stating that the optimum allocation of the resources of a society is not attained so long as it is possible to make at least one individual better off in his own estimation while keeping others as well off as before.