[jonathansizz]

I think neverminder meant that, amongst countries that separate, the larger of the new countries will generally be better off than their smaller neighbour. Your list doesn't address this point.

Examples would include Pakistan-Bangladesh; Czech Republic-Slovakia; and Sudan-South Sudan.

[legulere]

Your own list has a counterpoint: Bangladesh has a better HDI than Pakistan. Republic of Ireland also has an higher HDI than the UK and they were in much worse state than the UK when they became independent.