What would be the number you'd consider "flooding"? As soon the significant instability is introduced, it's too much. It depends on the effects, not on the numbers alone.
Good question and I couldn't tell you offhand - but I will stand by my disagreement with "+0.4% from migration is flooding" when "+0.9% from births" isn't.
Babies don't often bring foreign cultural norms and overwhelm social services. Which is why one might be flooded with migrants, but not babies, though there be more babies. It's why rain might cause flooding but not snow. The snow may cause a flood later, but not now.
