Except this meme is intentionally missusing the way percentages work. The fins census would just be of Finland, so even if their census had a 1% margin of error you'd only be missing 1% of fins, not the whole damn country. It's just meant to be funny.
There's also room for negative 0,9% in there, which could mean the nonexistant finns might drag someone else, like New Zealand, Estonia, Iceland or the Vatican into nonexistence with them.
Properly used, it can set the world a bit straighter
Used ineffectively or improperly, it can confuse and degrade