Why was Australia so rich?

Between 1870 and 1890 Australian incomes per capita were 40 percent or more above those in the United States. About half this gap is attributable to Australia's higher labor input per capita, and half to its higher labor productivity. The higher labor input is due in part to favorable demographic attributes and partly to a favorable workforce participation rate. The higher productivity results from an advantageous natural resource endowment. By 1914 the income lead over the U.S. had all but disappeared due to declines in Australia's advantages both in labor input per capita and in labor productivity.