One thing I read in college a zillion years that caught my interest, is that when a metro area gets larger than 400,000, it tends to have the infrastructure and offer services, that insure that it will continue to keep growing, and will no longer face the risk of having a substantial population decline. It would be interesting to see how that theory worked out, 50 years later and if it did not, why.
Many 400,000+ rust belt metros like Cleveland and Pittsburgh have lost population in this and other recent decades. I'd say no. I've been mapping historic population changes in CSAs and metros
here.
