If you look at large companies' accounts, they typically have inter segment reconciliations. Where intra-company trades are booked can be artificial. In the Chinese case, the city of Tianjin, e.g., which has a financial district, booked revenues from companies registered there but conducting no substantial business there in its own local GDP. This is akin to the state of Delaware including in its own GDP report (if there is such a thing) all companies registered there. But this inflation has no effect on the national GDP, which is aggregated over the businesses directly, so it does not matter how many provinces claim the businesses as their own. Hope this helps put things in context a little bit for you.