  Recent election surprises, regime changes, and political shocks indicate that
political agendas have become more fast-moving and volatile. The ability to
measure the complex dynamics of agenda change and capture the nature and extent
of volatility in political systems is therefore more crucial than ever before.
This study proposes a definition and operationalization of volatility that
combines insights from political science, communications, information theory,
and computational techniques. The proposed measures of fractionalization and
agenda change encompass the shifting salience of issues in the agenda as a
whole and allow the study of agendas across different domains. We evaluate
these metrics and compare them to other measures such as issue-level survival
rates and the Pedersen Index, which uses public-opinion poll data to measure
public agendas, as well as traditional media content to measure media agendas
in the UK and Germany. We show how these measures complement existing
approaches and could be employed in future agenda-setting research.
