Concentration ratio

Market structure

1. $C{R}_4$

2. $C{R}_8$

Oligopoly type I

$75\le C{R}_4$

-

Oligopoly type II

$75<C{R}_4\le 85$

or $\text{85}\le C{R}_8$

Oligopoly type III

$50<C{R}_4<85$

$\text{75}\le C{R}_8<85$

Oligopoly type IV

$35\le C{R}_4<50$

$45\le C{R}_8<75$

Oligopoly type V

$30\le C{R}_4<35$

or $40\le C{R}_8<45$

Competitive type

$C{R}_4<30$

or $C{R}_{\text{8}}<40$