Your metrics are flawed, what about innovation and design? If a country has companies that design and innovate new products, but they chose to produce them in another country, it will only show up in the manufacturing output of the production country. US and Japan used to produce everything until 1990s until it got too expensive and production moved offshore. Ultimately, production will will leave China also as it gets richer, and you will see decline in manufacturing and industrial output, which will be replaced by financial services, retail, IT and Tech etc etc, that is the natural order of things. Also as a country develops, there are lesser things left to build, Right now you are building bridges, highways etc etc, but what happens when you have already built them to every major and medium sized city? Will you build a road twice to the same place? As you develop, your construction sector will also grow at a smaller and smaller pace, again impating production of concrete, steel etc etc.