Go to a professional website. The balance sheet of supply and demand will list important data of supply and demand, including information such as inventory carried forward in the previous period, production, import, consumption, export and inventory carried forward in the current period. Supply and demand data can be queried on professional websites according to different products, but most professional websites charge fees. For example, chemical industry can go to Zhuochuang and Longzhong to check the daily, weekly and monthly supply and demand data and update them in real time.