Introduction: Cross-national policy
convergence: concepts, approaches
and explanatory factors
Christoph Knill
ABSTRACT Although
there is an increasing number of studies on policy conver
gence (in recent years especially in the context of Europeanization and globalization
research), we still have a rather limited understanding of this phenomen on. This
deficit can be not only traced back to a lack of empir ical findings, but is also the
result of the heterogeneous and partially inconsistent theoretical literature on
policy convergence. Although policy convergence constitutes a central concept in
comparative public policy, it is not always consistently used and mixed up with
related but not equivalent concepts. It is thus a basic objective of this paper to
clarify the analytical relationship between policy convergence and related conc epts
used in the literature. Moreover, different approaches for the assessment and
measurement of policy convergence will be presented. The paper concludes with a
brief discussion of causes of policy convergence.
KEY WORDS Europeanization; policy convergence; policy diffusion; policy
transfer; public policy.
The comparative analysis of public policies across countries is a well-developed
research area
with a long tradition in political science. One of the major debates
in this research field centres on the question as to whether and why different
countries develop similar policies over time. In the literature, there are two
different answers to this question.
There are numerous studies that emphasize a striking degree of policy conver-
gence; i.e. the development of similar or even identical policies across countries
over time. For years, political scientists have been attracted by this phenomenon
and its underlying causal factors (for an overview of the policy convergence
literature, see Bennett 1991; Drezner 2001; Heichel et al. 2005). At the same
time, however, there are many studies (typically in the tradition of the new
institutionalism) that modify or even challenge the general expectation of
cross-national policy convergence. Emphasizing important differences in national
institutions and opportunity structures for domestic actors, these studies find
diverging rather than converging policy developments across countries.
Erschienen in: Journal of European Public Policy, Special Issue ; 12 (2005), 5. - S. 764-774
Konstanzer Online-Publikations-System (KOPS)
URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-18622
This debate of convergence versus divergence of national policies is closely
related to the booming research industry on globalization and Europeanization.
Does the strong growth of economic and institutional interlinkages between
nation states lead to increasingly similar policies across countries? Or is the
search for convergence emerging from the domestic impact of globalization
and European integration ‘an impossible quest’ (Dimitrova and Steunenberg
2000: 201), as domestic responses to global or European challenges are strongly
influenced by existing domestic structures and institutions (see, for example,
Caporaso et al. 2001; He
´
ritier et al. 2001; Knill 2001)?
This brief discussion clearly shows that we still have a rather limited under-
standing of the phenomenon of policy convergence. What explains the adoption
of similar policies across countries over time? Under which conditions can we
expect that domestic policies converge or rather develop further apart? Why
do countries converge on some policies, but not on others? What is the direction
of policy convergence? Do national policies converge at the regulatory top or
bottom, and why?
Although a number of factors have been suggested in order to account for the
mixed empirical evidence of both convergence and divergence, including the
role of international organizations, regulatory competition between nation
states, or capacities for national policy adjustment, we still have limited knowl-
edge about the causes and conditions of cross-national policy convergence. This
deficit can be not only traced back to a lack of empirical findings, but is also the
result of the heterogeneous and partially inconsistent theoretical literature on
policy convergence. Although policy convergence constitutes a central concept
in comparative public policy, it is not always consistently used and mixed up
with related but not equivalent concepts. It is therefore hardly surprising that
the mechanisms and conditions affecting the degree of cross-national policy
convergence are not yet well understood (cf. Seeliger 1996).
It is the objective of the following contributions to improve our understand-
ing of policy convergence and its causes. This presupposes a clear definition of
the concept of convergence. In the following sections, I will thus first clarify the
analytical relationship between policy convergence and related concepts used in
the literature. Moreover, different approaches for the assessment and measure-
ment of policy convergence will be presented. I conclude with a brief discussion
of the causes of policy convergence to which the following articles are related.
Unless explicitly acknowledged, the contributions follow the definitions and
assessment criteria as defined in the following sections.
POLICY CONVERGENCE AND RELATED CONCEPTS
While there is a broad consensus on the definition of convergence as ‘the ten-
dency of societies to grow more alike, to develop similarities in structures, pro-
cesses, and performances’ (Kerr 1983: 3), the empirical and theoretical
assessment of policy convergence is generally hampered by the use of different,
partially overlapping concepts (Tews 2002). Policy convergence is equated with
765
related notions, such as isomorphism, policy transfer or policy diffusion. This
terminological variety often coincides with analytical confusion.
This becomes most apparent when focusing on the concept of policy transfer
(Dolowitz and Marsh 1996, 2000; Radaelli 2000; Rose 1991). Dolowitz and
Marsh (2000: 5) define policy transfer as ‘processes by which knowledge
about policies, administrative arrangements, institutions and ideas in one
political system (past or present) is used in the development of policies, admin-
istrative arrangements, institutions and ideas in another political system’. Policy
transfer is therefore concerned with processes rather than results. Moreover, it
prescribes a development that might, but need not, lead to cross-national
policy convergence. Policy transfer is not restricted to merely imitating policies
of other countries, but can include profound changes in the content of the
exchanged policies (Kern et al. 2000; Rose 1991).
Similar to transfer, policy diffusion typically refers to processes (rather than
outcomes) that might result in increasing policy similarities across countries,
hence leading to policy convergence (Elkins and Simmons 2005: 36). Diffusion
is generally defined as the socially mediated spread of policies across and within
political systems, including communication and influence processes which
operate both on and within populations of adopters (Rogers 1995: 13). Most
of the diffusion literature is characterized by this approach. Diffusion studies
typically start out from the description of adoption patterns for certain policy
innovations over time. In a subsequent step, they analyse the factors that
account for the empirically observed spreading process. According to this
concept of diffusion, no distinction in different forms of ‘spread mediation’
or ‘influence processes’ is made. Hence, from this perspective, policy diffusion
is not restricted to the operation of specific mediation mechanisms, but includes
all conceivable channels of influence between countries, reaching from the
voluntary adoption of policy models that have been communicated in the
international system, diffusion processes triggered by legally binding harmoni-
zation requirements defined in international agreements or supranational
regulations, to the imposition of policies on other countries through external
actors.
In contrast to this definition, however, some authors suggest a narrower focus
of the concept, explicitly restricting diffusion to processes of voluntary policy
transfer (Kern 2000; Busch and Jo
¨
rgens 2005). Consequently, diffusion is con-
ceived as a distinctive causal factor that drives international policy convergence
rather than a general process that is caused by the operation of varying (both
voluntary and coercive) influence channels. Following this approach, Busch
and Jo
¨
rgens distinguish three mechanisms of policy convergence: international
harmonization (legal obligation from international or supranational agreements
deliberately agreed by the involved countries in multilateral negotiations),
imposition of policies, and policy diffusion (where national policy-makers
voluntarily adopt policy models that are communicated internationally).
We are thus confronted with two different conceptions of policy diffusion.
On the one hand, the concept describes the process of spreading policies
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across countries with the possible result of cross-national policy convergence,
regardless of the causal factors that are driving this development (e.g. regulatory
competition, international harmonization, imposition). On the other hand, dif-
fusion is conceived as a distinctive causal factor leading to policy convergence by
voluntary (in contrast to obliged or imposed) transfer of policy models.
Both conceptions of diffusion are analytically well grounded and applied in
the literature; it is therefore more important to point out their differences rather
than arguing in favour of one or the other approach. Nevertheless, the following
considerations as well as the contributions to this volume (except the article by
Busch and Jo
¨
rgens) follow the first definition, conceiving of diffusion as a
process that can be triggered by a broad range of causal factors.
Policy diffusion and policy transfer share the assumption that governments
do not learn about policy practices randomly, but rather through common
affiliations, negotiations and institutional membership (Simmons and Elkins
2004). Both transfer and diffusion processes hence require that actors are
informed about the policy choices of others (Strang and Meyer 1993: 488).
Given these conceptual overlaps, diffusion is often equated with policy transfer
(Kern 2000; Tews 2002). Notwithstanding these conceptual overlaps, however,
analytical differences between diffusion and transfer should not be overlooked.
Diffusion studies typically start out from a rather general perspective. While
analyses of policy transfer investigate the underlying causes and contents of
singular processes of bilateral policy exchange, the dependent variable in diffu-
sion research refers to general patterns characterizing the spread of innovations
within or across political systems. The diffusion literature focuses more on the
spatial, structural and socioeconomic reasons for particular adoption patterns
rather than on the reasons for individual adoptions as such (Bennett 1991:
221; Jordana and Levi-Faur 2005). Diffusion studies often reveal a rather
robust adoption pattern, with the cumulative adoption of a policy innovation
over time following an S-shaped curve (Gray 1973). Relatively few countries
adopt an innovation during early stages. Over time, the rate of adoption
increases, until the process gets closer to saturation, and the rate slows down
again.
From these considerations it follows that policy transfer and policy diffusion
differ from policy convergence in important ways. First, differences exist with
respect to the underlying analytical focus. While diffusion and transfer are con-
cerned with process patterns, convergence studies place particular emphasis on
effects. Transfer and diffusion thus reflect processes which under certain circum-
stances might result in policy convergence. This does not imply, however, that
the empirical observation of converging policies must necessarily be the result of
transfer or diffusion (Drezner 2001). It is well conceivable that policy conver-
gence is the result of similar but relatively isolated domestic events. Second,
the concepts differ in their dependent variable. Convergence studies typically
seek to explain changes in policy similarity over time. By contrast, transfer
studies investigate the content and process of policy transfer as the dependent
variable, while the focus of diffusion research is on the explanation of adoption
767
patterns over time (Elkins and Simmons 2005; Jordana and Levi-Faur 2005;
Levi-Faur 2005; Gilardi 2005).
The particular focus underlying the analysis of policy convergence places it in
close proximity to the concept of isomorphism which has been developed in organ-
ization sociology. Isomorphism is defined as a process of homogenization that
‘forces one unit in a population to resemble other units that face the same set
of environmental conditions’ (DiMaggio and Powell 1991: 66). The central
question underlying studies on isomorphism refers to the mechanisms through
which organizations become more similar over time. There is thus a broad
overlap between studies on policy convergence and isomorphism, with the
major difference between the two concepts being on their empirical focus. The
literature on isomorphism concentrates on increasing similarity of organizational
and institutional structures and cultures. Studies on policy convergence, transfer
or diffusion, by contrast, focus on changes in national policy characteristics.
Following the above considerations, policy convergence can be defined as any
increase in the similarity between one or more characteristics of a certain policy
(e.g. policy objectives, policy instruments, policy settings) across a given set of
political jurisdictions (supranational institutions, states, regions, local auth-
orities) over a given period of time. Policy convergence thus describes the end
result of a process of policy change over time towards some common point,
regardless of the causal processes.
TYPES OF POLICY CONVERGENCE
Having discussed the relationship between policy convergence and other
analytical concepts that are often used synonymously in the literature, we still
have to address the question of how convergence can be measured and evaluated
empirically. The most basic way of assessing policy convergence is to analyse the
extent to which the policies of countries have become more similar to each other
over time. However, depending on the underlying criteria for the assessment of
similarity change over time, different types of policy convergence are applied in
the literature.
Table 1 Policy convergence and related concepts
Policy
convergence Isomorphism
Policy
transfer
Policy
diffusion
Analytical
focus
Effects Effects Process Process
Empirical
focus
Policy
characteristics
Organizational
structures
Policy
characteristics
Policy
characteristics
Dependent
variable
Similarity change Similarity
change
Transfer content
transfer process
Adoption pattern
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