Profits should not be calculated on a subsidiary basis, period. Profits should be calculated as the global profits (of the main form and all its subsidiaries),

Profits should not be calculated on a subsidiary basis, period. Profits should be calculated as the global profits (of the main form and all its subsidiaries), multiplied by the ratio of revenue in that country vs global revenue. One reason this is not implemented by some countries is this: the USA (or Ireland) wish to tax Apple on as much of their their global profits as possible, and France/Germany want to tax Airbus on as much of their their global profits as possible, not only the profits made in these countries. And the no double-taxation principle means that profits can only be taxed in one place.