Mass migration is an incredibly asymmetric gamble. If it goes well, you boost GDP by a few percentage points.
If it goes poorly, you end up with a permanent foreign body, constant conflict between groups, massive resource transfers, and slow reshaping of society to manage it.
BREAKING:
Young second and third-generation migrants continue attacking schools across France.
A group of masked youth just stole a fire truck in Marseille, vandalized it and set it on fire