We study the resource allocation problem from the lens of welfare economics. The focuses are on two critical criteria: efficiency and fairness. We consider a broad class of resource allocation problems, and quantitatively analyze the tradeoffs between efficiency and fairness by employing the approach of approximation. We show nearly optimal bicriteria approximation Pareto curves, which give an explicit answer to the question that whether there exists an allocation that achieves (almost) any targeted efficiency and fairness.