The Winemakers Federation of Australia says the industry is midway toward correcting a national oversupply of wine grapes. The latest vintage survey showing the national crop is 12 per cent down on the year before.A 200,000-tonne drop in the latest year follows a 100,000-tonne decline the year before. Chief executive of the Winemakers Federation Steve Strachan says the downward trend will need to continue for another few years.