这是一个复合句。主句:Economists are interested in all the factors--主 (economists) 系 (are) 表 (interested in all the factors) 结构;
从句1 定语从句修饰先行词factors:that can help predict the extent-- that关系代词作主语的主 (that)谓 (can help predict)宾 (the extent)结构;
从句2 还是定语从句修饰先行词extent: to which a price change will affect supply and demand in the market--主(a price change) 谓 (will affect) 宾 (supply and demand) 结构, to which 含有关系代次的介词短语作状语。