Because a group of steel, aluminium coated steel group non-centralize, which could be modified by the way the price is based on prices quoted only the first group granted material is likely higher rates every year.
The group of steel, aluminum, iron group. non-centralize Which can not be adjusted The price will be based on the first leg of the bidding group, clad material, which is likely due to increasing annually.
Since the group of aluminum coated steel is a steel group non-centralize which cannot be adjusted. Based on the price of the first bid only, which material group this likely prices rise every year.