The U.S. Department of Agriculture on Friday said by resolving dozens of trade issues in 2012, it has witnessed a freeing of about $4 billion in U.S. agricultural and forestry products. "USDA staff are monitoring more than 160 markets to ensure an open system of trade, free from unwarranted and unjustified barriers," said U.S. Agriculture Secretary Tom Vilsack in a statement. "Since 2009, USDA has acted to remove hundreds of unfair barriers to trade for American compa...