the collapse will unfold from the periphery to the center

An indication is the number of failed states.

There are about 190 nation-states in the world.

About 20 of them are failed states:

Afghanistan
Burkina Faso
Cameroon
Central African Republic
Democratic Republic of the Congo
Ethiopia
Iraq
Lebanon
Mali
Mozambique
Myanmar
Niger
Nigeria
Somalia
South Sudan
Sudan
Syria
Ukraine
West Bank and Gaza
Yemen

Here’s how you can follow the process of collapse:

Come back here in ten years and you’ll see that the number of failed states has increased to 25.

Come back in twenty years and you’ll see that the number of failed states has increased to 30.

Come back in thirty years and you’ll see that the number of failed states has increased to 35.

Come back in forty years and you’ll see that the number of failed states has increased to 40.

Come back in fifty years and you’ll see that the number of failed states has increased to 45.

Come back in sixty years and you’ll see that the number of failed states has increased to 50.

Come back in seventy years and you’ll see that the number of failed states has increased to 55.

Come back in eighty years and you’ll see that the number of failed states has increased to 60.

That’s about 31% of all the countries, encompassing about 47% of the human population.

So by 2104 about 47% of all people will be living within a failed state and you will start to hear murmurings about civilizational collapse.