Editing Oligopoly (section)

=== Other descriptions ===
[[Market power]] and [[market concentration]] can be estimated or quantified using several different tools and measurements, including the [[Lerner index]], [[stochastic frontier analysis]], New Empirical Industrial Organization (NEIO) modeling,<ref name="LopezHeAzzam" /> as well as the [[Herfindahl-Hirschman index]].<ref name="EricssonTegen" /> As a quantitative description of oligopoly, the four-firm [[concentration ratio]] is often utilised and is the most preferable ratio for analyzing [[market concentration]].<ref>Sys, C. (2009). Is the container liner shipping industry an oligopoly?. ''Transport Policy'', ''16''(5), 259-270.</ref> This measure expresses, as a percentage, the market share of the four largest firms in any particular industry. For example, as of fourth quarter 2008, the combined total market share of Verizon Wireless, AT&T, Sprint, and T-Mobile comprises 97% of the U.S. cellular telephone market.<ref>{{Cite web |last=Chitkara |first=Hirsh |title=US Cellular and Charter are challenging the Big Four's dominance in the US wireless market |url=https://www.businessinsider.com/us-cellular-charter-challenge-big-four-in-us-wireless-market-2019-10 |access-date=2023-04-09 |website=Business Insider |language=en-US |archive-date=19 April 2021 |archive-url=https://web.archive.org/web/20210419102843/https://www.businessinsider.com/us-cellular-charter-challenge-big-four-in-us-wireless-market-2019-10 |url-status=live }}</ref>