I've been hearing about how experts are skeptical of China's GDP reports for years and years. This skepticism goes back decades, probably to 1990, or earlier? I recommend you do your own investigation, get a feel for the zeitgeist yourself – anything that predates the internet takes more effort than I'd put in, particularly to make a point as abstract as I'd like to make today.
If the numbers were closer to 5% than 10% growth for decades, any idiot with a tally counter or a satellite could figure out the real GDP number was lower. At some point the difference is bigger than e.g. the difference between The United States (doing pretty well, on top) and Italy (not doing amazing at the moment, never as wealthy as America). 50+% differences aren't subtle, and the world provides plenty of countries of medium wealth to compare and contrast against.
I agree that the numbers the PRC releases aren't of amazing quality. They (very probably) overstate growth, and under-report information that would help understand systemic risk – the shadow banking sector's over-leveraged spending alone is material and massive and not good news – and largely hidden from reports.
And I've been saying for years that until they take corruption and money laundering seriously enough that I cannot reliably infer someone is worth hundreds of millions of dollars because they're a relative of Xi Jinping, it's unlikely their capital controls will capture truth with the fidelity major economies are expected to. Right now corruption is targeted piecemeal, when it's targeted at all – what they need are real systems that can observe the economy as it happens (that's right, used s a verb, not a noun) – without being so invasive as to push people into shadow banking.
But at the end of the day, who's being fooled? They could probably only have goosed 0.3% to growth every year on average without someone noticing and producing meaningful proof of falsehood by now – or at least showing that foreign firms are getting crushed in comparison there. And 0.3% is not nearly as big as the difference between China and Europe/USA/Japan. It truly seems to me this isn't lying per se, but just simple error – and if that's the case, maybe we should stop imagining the story as a malicious and lying government – and imagine it as a flawed, corrupt, unaccountable government.