"While more think-tanks are appearing around the globe, individual think-tanks themselves are simultaneously globalising [by] executing global expansion strategies," found the study, produced by James McGann, director of the 'Think-Tanks and Civil Societies Program' at the Philadelphia-based institution.
While "think-tanks can be seen as one of the main policy actors in democratic societies that assure a pluralistic, open and accountable process of policy analysis, research, decision-making and evaluation," they are can also be considered "as a euphemism for special interest groups that have their own political agendas," McGann warned.
Today there are over 6,300 think-tanks operating in 169 countries, according to the study, a proliferation which it claims has "exponentially increased the potential for international communication, information-gathering, and new and creative policy analysis".
However, "not all think-tanks have the financial, intellectual and legal independence that enables them to inform public decision-making," the study cautions, concluding that the problem is "most acute" in developing and transitional countries, where financial and legal support is limited.
Worldwide, North America and Western Europe "dominate the scene" with 56% of think-tanks, while the 'Middle East and North Africa' (4%) and Africa (8%) have the fewest.
"The number and overall impact of policy research organisations have been growing and spreading," McGann’s research found, stressing that while think-tanks are just one of many civil society actors in a country, "they often serve as catalysts for political and economic reform".
Europe is home to 1,750 think-tanks, or 28% of the world’s total, the study reveals. Of these, 285 are based in the UK, significantly more than in second-placed Germany (190) or third-placed France (168).
The researchers rank Chatham House (UK) as the number one non-US think-tank in the world, followed in second and third place by Transparency International (Germany) and the International Crisis Group (Belgium) respectively: although the latter two could also be seen as pressure groups.
The Belgium-based Centre for European Policy Studies (CEPS) is the first EU-centric think-tank to make the list, in ninth position.
In the Western European ranking, CEPS makes fourth position, with Chatham House topping the list. The Centre for European Reform (CER) in London came 15th.
Each think-tank was rated according to a wide variety of criteria, including research output (number of publications, conferences held, web hits, mentions in respected media), the degree to which its policy recommendations are adopted or considered by policymakers, access to political elites, ability to retain elite scholars and analysts, and size of its financial resources.