In other words, the market position of the dominating firm can be provided with its ability to attract the buyer, at insufficient sales volume of other firms. In this case small firms have to adapt to the leader's price in order that they had an opportunity to have, at least a small share of the market.
Price discrimination is favorable only when price elasticity differs in the served markets. It can be proved easily, I use a formula of the limit income. At any price of MR=P (1+1/Edb). It is fair for the limit income on each of the served markets. For maximizing profit the limit income has to be equal. Therefore: Pa (1+1/Eda) =Pb (1+1/Edb)
But many economists consider that such structural proof as degree of concentration or Gerfendal's index is insufficient for definition of degree of competition of the market. Moreover, they claim that it is necessary to pay, first of all, attention to market behavior of firms.