There is only one calculation for a failed state, and it is this: If the nation...

There is only one calculation for a failed state, and it is this:

If the nation or group of people you belong to cannot produce enough competent adults to maintain itself, its infrastructure, and its economy while continuing to produce future generations, then you are living in a failed state on its way to extinction.

Immigration from less successful groups of people will only add burdens to your productive people, reduce your fertility, and speed up the collapse.