I also worked as a canvasser in 2019 and 2020 for the US census and, while we were about as thorough as you could reasonably get, the whole operation made me somewhat skeptical of official statistics in general. 2020 in particular was a bit of a disaster due to the pandemic and when the statistics were published, a bunch of mainstream news outlets published stories about certain areas experiencing "population decline" and all I could think was that those were actually the areas where the census didn't manage to count everyone.
And how long does it take for that central registry to be informed when somebody has emigrated from the country without informing the government? Five years? Ten?
In e.g. Germany that requires a signed statement from the landlord, and the ability to receive mail at that address. If you can't receive mail at your own address, it'd be noticed and reported within at most 5 years. I actually believe it'd be the national health insurance that'd be the first to notice & report you missing, as having health insurance is mandatory (even if you continue paying them, they'd notice it once they can't send you a replacement card).