▁= ▁I [ Total ▁consumption ▁> ▁ Σ i ≠ x C i ▁] ▁ ▁where ▁the ▁sum ▁of ▁capac ities ▁is ▁taken ▁over ▁all ▁supp liers ▁apart ▁from ▁x . ▁ ▁The ▁P SI ▁is ▁a ▁binary ▁indicator ▁that ▁can ▁be ▁calculated ▁hour ly . ▁If ▁the ▁supp lier ▁C x ▁is ▁needed ▁to ▁supply ▁the ▁demand , ▁it ▁is ▁p iv otal ▁and ▁the ▁index ▁takes ▁the ▁value ▁" 1 ". ▁If ▁he ▁is ▁not ▁p iv otal , ▁it ▁takes ▁the ▁value ▁" 0 ". ▁ ▁Res id ual ▁Supp ly ▁Index ▁( R SI ) ▁The ▁Res id ual ▁Supp ly ▁Index ▁is ▁a ▁simple ▁and ▁effective ▁tool ▁in ▁monitoring ▁market ▁power . ▁It ▁is ▁the ▁non - binary ▁alternative ▁to ▁the ▁P SI . ▁The ▁Res id ual ▁Supp ly ▁Index ▁is ▁expressed ▁as : ▁ ▁R SI ▁= ▁( Σ n 1 ▁Ci ▁- ▁C x )/ D ▁where ▁C x ▁is ▁the ▁capacity ▁of ▁the ▁anal ys ed ▁supp lier ▁and ▁the ▁sum ▁of ▁Ci ▁the ▁capacity ▁of ▁all ▁supp liers , ▁and ▁D ▁is ▁demand . ▁ ▁As ▁the ▁estimated ▁R SI ▁exceed s ▁ 1 0 0 %, ▁the ▁R SI ▁gives ▁an ▁indic ation ▁that ▁the ▁supp lier ▁x ' s ▁potential ▁to ▁impact ▁price ▁is ▁falling . ▁With ▁a ▁R SI ▁smaller ▁than ▁ 1 0 0 %, ▁the ▁supp lier ▁being ▁analyz ed ▁begins ▁to ▁become ▁more ▁' p iv otal ' ▁and ▁thus ▁could ▁potentially ▁pract ise ▁market ▁power .