The US has also been going down the international ladder for much of the last 50 or 80 years, yes? Japan was once a poor country. Singapore, Hong Kong, Taiwan, and Korea were once much poorer than they are now. Nearly all of Europe is richer now, relative to America, than it was at any time 1900-1980? 100 years ago America had the highest wages in the world, yes? I should think there must be at least 40 countries that are richer now, relative to America, than they were in, say, 1920, or 1930, or 1960, or 1970.
But still, as to why Australia is rich, a large part of it must be that it is an English speaking country, with an English speaking political culture. When was the last time Australia had a civil war? When was the last time Australia had a coup de etat? The English speaking peoples were the first peoples to have a modern revolution, they had theirs in the 1640s, the French waited till the 1780s. The stability of modern democracy matters. If a country can grow 1% a year for a century it ends up with a lot more economic growth than another country that grows 50% one decade, then loses 40% the next decade because of civil war, then grows another 50% the next decade because of an oil boom, then loses another 40% the next decade because of social collapse and political instability.
Lawrence Krubner