Why where there are no differences among countries in the basic capabilities at producing goods, other bases for trade among them may still exist?

Why where there are no differences among countries in the basic capabilities at producing goods, other bases for trade among them may still exist?

First, patterns of demand may differ among nations. Second, trade may occur out of economies of scale，that is，the cost advantages of large-scaleproduction.Third, trade takes place because of innovation or style.