The concept does not take into account changes in the productivity of a resource. The concept means that if a bushel of wheat bought a shirt in the past, that it should continue to buy a shirt today and shirts are much more expensive today.
Parity means equality of value, and there are actually no problems with the concept.
Consists of efforts that effect the transfer of production. None of the above. The part of the quantity provided by nature that is used for want satisfaction. The total quantity of the resource provided by nature. A derived supply.