Input-output analysis is one of a set of related methods which show how the parts of a system are affected by a change in one part of that system. Input-output analysis specifically shows how industries are linked together through supplying inputs for the output of an economy. Suppose there are only two industries producing Coal and Steel. Coal is required to produce steel and some amount of steel in the form of tools is required to produce coal. Suppose the input requirements per ton output of the two products are: