Production possibility frontier is drawn on the assumption that the given resources and technology are fully as well as efficiently utilized. so if resources are inefficiently utilized in an economy, it implies that the economy is not maximizing its output with the given resources. It is a situation when the concerned economy is not operating on the production possibility curve, but is somewhere within the production possibility frontier. So that, it it possible to increase the level of output of Goof-X, or Good-Y or both X and Y.