  From a liberal perspective, pluralism and viewpoint diversity are seen as a
necessary condition for a well-functioning democracy. Recently, there have been
claims that viewpoint diversity is diminishing in online social networks,
putting users in a "bubble", where they receive political information which
they agree with. The contributions from our investigations are fivefold: (1) we
introduce different dimensions of the highly complex value viewpoint diversity
using political theory; (2) we provide an overview of the metrics used in the
literature of viewpoint diversity analysis; (3) we operationalize new metrics
using the theory and provide a framework to analyze viewpoint diversity in
Twitter for different political cultures; (4) we share our results for a case
study on minorities we performed for Turkish and Dutch Twitter users; (5) we
show that minority users cannot reach a large percentage of Turkish Twitter
users. With the last of these contributions, using theory from communication
scholars and philosophers, we show how minority access is missing from the
typical dimensions of viewpoint diversity studied by computer scientists and
the impact it has on viewpoint diversity analysis.

Social and Information Networks;Computers and Society;Physics and Society