A larger economy is more diversified, diversity will create a regression to the mean. And sheer scale creates momentum -- it takes a lot to accelerate and a lot

A larger economy is more diversified, diversity will create a regression to the mean. And sheer scale creates momentum -- it takes a lot to accelerate and a lot to decelerate. Less diversified economies show wider swings. Australia rode on the sheep's back for most of a century, these days the country's fortunes closely track the prices of coal and iron ore. Still, from indicators like number of public companies, market capitalisation and so forth, the USA's economy is growing less diverse at the moment.