''Considering that over 2/3 of the people in Australia were born...

''Considering that over 2/3 of the people in Australia were born here, why would that be a surprise?''

you assume - again, incorrectly

take Spain as an example - the vast majority of people who live in Spain, were born in Spain ---------- way over 80%

but, the main groups who leave Spain to go elsewhere are NOT Spanish born -

the are from other nations

You can check that now that you are able to research -

what that suggests is there is a difference between a place like Spain and a place like Australia

for Australia - Australians are the largest group packing up and leaving
for Spain - it's very much not so

that suggests that Australians far more so think that other places are better