Because an open and free media landscape with divergent opinions and ideas is a key aspect in democratic societies, media pluralism is considered highly important with regard to media policy. Given the foundation of pluralism in legislation on media concentration, the theoretical background of media pluralism will be discussed briefly. The Mediamonitor’s model for analyzing media markets is presented in a break-down of the different aspects of pluralism.
Pluralism refers to diversity in the most general sense. However, the concept includes a number of aspects and has been interpreted from different perspectives, and consequently is measured by using many different qualitative and quantitative criteria. In analyzing the concept of pluralism, two perspectives have to be mentioned in this regard: internal and external pluralism.
Internal pluralism reflects how social and political diversity are reflected in media content. That is, the representation of different cultural groups in the media as well as divergent political or ideological opinions and viewpoints. Internal pluralism plays an important role in news and public affairs coverage, and also for public broadcasting and media landscapes dominated by one (monopoly) or two (duopoly) players. Governments can not only stimulate internal pluralism by facilitating public service broadcasting, but also by means of financial support such as grants, press funds, reduced tax rates, etc.
Whereas internal pluralism focuses on media content, external pluralism covers the number of owners, media companies, independent editorial boards, channels, titles or programmes. This type of pluralism is also known as the ‘plurality’ of suppliers. From the perspective of the ‘free marketplace of ideas’, competition between these media content suppliers is considered to be essential in order to ensure a free choice of media content and the availability of a wide variety of opinions and ideas. Policies on media concentration are most concerned with the market power that owners or companies may gain and the subsequent possibility of exerting influence.
The Mediamonitor focuses on external pluralism, hereafter referred to as media diversity , and does not address media content specifically. Due to the various aspects of media content research, the Mediamonitor is not able to regularly assess the diversity of media content, only incidentally in thematic studies. The Dutch News Monitor  does however regularly investigate the coverage of remarkable news events (or ‘hypes’) as well as the representation of political parties and politicians in newspapers, on television and on news sites.
In further breaking down media diversity, the Mediamonitor uses a model to analyze the media markets that takes into account all steps of the media production process. Media concentration (the opposite of diversity) can manifest itself in the value chain of content creation,content packaging and/or content delivery (see figure below). The value chain is shown as having three main components: source (supplier), content and consumer (audience).
The most common type of media concentration is horizontal concentration in one link of the production value chain. A second type of media concentration is vertical concentration in two or more links of the media value chain. A third form of media concentration is diagonal concentration (i.e. cross-media ownership), that is a publisher or a broadcaster entering into other media types in addition to its usual operations; for instance a publisher that becomes active in a radio or television station in addition to a daily paper.
Horizontal concentration and cross-media ownership are of the greatest concern in policies that strive to safeguard a minimum number of suppliers in one or more media markets. The Monitor maps and visualizes changes in these types of ownership, monitors relationships in the media sector and outlines trends that may influence the independence and diversity of the media.
In relation to the supply chains of the media production process, various types of media concentration can be identified that may occur in media markets, namely:
a) supplier concentration,
b) editorial or programming concentration,
c) concentration of media content and
d) audience concentration.
The figure below shows an overview of the available measurements for each type of media concentration.
Supplier or ownership concentration
In the Mediamonitor, horizontal supplier concentration is assessed on the basis of ownership relationships between media enterprises and their market shares of the respective markets. The degree of horizontal supplier concentration is measured by the Herfindah-Hirschman Index (HHI). Based on the HHI index, the degree of media concentration on a specific market can be labelled as follows:
- Unconcentrated media market: a market that statistically matches a market with more than ten equally large media enterprises;
- Moderately concentrated media market: a market that statistically matches a market with more than five and less than ten equally large media enterprises;
- Highly concentrated media market: a market that statistically matches a market with five or less equally large media enterprises.
In addition to the HHI concentration index, the Monitor also reports C1, C2 and C3. These indexes refer to the market share(s) of the market leader (C1), of the two largest media companies (C2), and of the three largest media companies (C3).
As for cross-media ownership, the Monitor follows developments among key players in the media market. This type of concentration is considered to be highly important given the ongoing convergence of information and communication technologies.
Editorial or programming concentration
In addition to supplier concentration, editorial and programming concentration may manifest itself in media markets. This is the case when the editorial staff or programme makers cannot independently produce the content of their titles or channel. The Monitor takes the number of editorially independent titles as an (inverse) indicator of editorial concentration (also to be labelled as ‘title concentration’). The number of independent broadcasting channels is used as the (inverse) indicator of programming concentration (also to be labelled as ‘channel concentration’). The opposite of editorial / programming concentration is editorial / programming competition.
Concentration of media content
Media diversity is the degree to which media content is heterogeneous. Assessing media diversity requires media content analysis. Media diversity manifests itself in two different forms, as reflective diversity and open diversity. Reflective diversity is the extent to which existing population preferences are proportionally represented in media content. Open diversity is the extent to which divergent preferences and opinions are quantitatively equally (i.e. statistically uniformly) represented in the media.
A concept that is closely related to media diversity is media profusion. Media profusion may be defined as the extent to which the supply of media content to a media market exceeds the audience’s actual consumption of media content. Media profusion adds the dimension of choice to diversity, to indicate that a sheer increase in media supply in itself enhances the possibility for media consumers to choose from a variety of media products and services.
The Mediamonitor published a thematic study on profusion  in 2005 and mapped all the news published in several news titles, programmes and websites during one day in 2009 .
Supplier concentration, editorial concentration and diversity are concepts on the supply side of media markets. On the demand side of markets we may measure audience (or exposure) concentration: the degree to which audience media preferences and usage are distributed over channels and titles. This is measured by means of media consumption time and a medium’s reach. By comparing the supply and demand on media markets, the match between media offered and users’ preferences may be assessed.