请问式子里跟1长得差不多的那个符号是什么意思呀？文章附录里的一个式子，没写代表什么。原文：We use input-output accounts in the United States (in 2002,Stewart et al., 2007) to construct a measure of factor use along the production chain,sp =Pi αp,qri,q1p(i)=q/Pi αp,q1p(i)=q, where αp,q is the contribution of product q inthe production of p.