USDA's weekly crop ratings report can  be a valuable tool if market participants use them as a guide and not as a scientifically factual, reliable yield-estimating tool. Unfortunately, that is what they have become. Their power was again demonstrated by the market actions on Tuesday and Wednesday.Every year at the start of the growing season, WPI writes an analysis of the value of USDA’s weekly crop progress report, and this is it for 2017. Those reports are released every Monday throughout the planting, growing and harvesting seasons with estimates of the progress made as well as crop condition ratings. They are a valuable source of information to the trade, especially the planting and harvest progress sections. The crop ratings can a...