The Laakso–Taagepera index (Laakso and Taagepera, 1979) has become the most commonly used measure to specify the ‘effective’ number of political parties in a party system where parties vary substantially in their vote and/or seat shares. It is well known that the Laakso–Taagepera index is the inverse of the even more widely used Herfindahl–Hirschman index of concentration (Hirschman, 1945; Herf...

Abstract The topic of finding effective strategies to restrain epidemic spreading in complex networks is current interest. A widely used approach for containment the fragmentation contact through immunization. However, due limitation immune resources, we cannot always fragment network completely. In this study, based on size distribution connected components network, designed a risk indicator o...

The Herfindahl-Hirschman Index is one of the most commonly used indicators to detect anticompetitive behavior in industries. In fact, an increase in the value of the index is usually interpreted as an indicator of actions which may lessen competition or even create a monopoly. In this paper we show that this is not always the case. If all firms cooperate, then the index cannot be used since it ...

When major investors own shares in multiple firms in the same industry, the cross ownership changes competitive interests and moves the equilibrium closer to the monopoly solution. In the presence of cross ownership, the traditional measure of industry concentration, the Hirschman-Herfindahl Index, fails to accurately reflect the level of competition in the market. We extend the literature on c...

BACKGROUND Continuity of care (COC) has received attention over the past decade. COC has also become increasingly important for hospital managers and policy makers because of competitive health care market conditions. The purpose of this study was to assess the association between hospital charges and patients' continuity of care-assessed by three indices of continuity of care-among outpatients...