This reminds me of the story where the Secretaries of Education of the German states recently found out that their projection for the number of first-graders in 5 years was off by about 400,000 (in a country of 80 million people).
Because, y'know, it's not like you could get any reliable data on how many people in your country will be six years old, five years from now...
How many people born in 2016 will come in, and how many will leave? (Hopefully child mortality is low enough and will stay low enough so as to not be relevant.)
400,000 is a 40% error on a population of 80 million with a life expectancy of 80 years. Unless 45% of recent asylum seekers were 6 years old, or unless 40% of 6 year olds emigrated (I don’t know which way the error went), that is too large a surprise to be so easily forgiven.
I never said a single factor fell into the 400k figure.
I'm also highly skeptical of the figure itself, as the total number of enrolled 6-year-olds is only 675k (97% of population) in 2012 (the last year the number was available), and for the years prior, it was pretty stable (+/- 50k). [1]
Being off by an order less than that makes some sense, but being off by 60% in a pretty stable country seems completely improbable.
Because, y'know, it's not like you could get any reliable data on how many people in your country will be six years old, five years from now...