By analyst By Cecilia Jamasmie Iron ore will sink back below $50 a tonne by 2019 as global supply continues to increase, steel inventories swell and Chinese demand dwindles, according to Australia, the world’s top exporter, which released its revised outlook just a day after the country’s largest port reported a jump in shipments for August. Forecast comes only a day after the country’s largest port reported a jump in iron ore shipments for August.