Dyadic Representation in a Westminster System

AuthorBenjamin E. Lauderdale,Chris Hanretty,Nick Vivyan
Date01 May 2017
Published date01 May 2017
University of East Anglia
London School of Economics and Political Science
Durham University
Dyadic Representation in a
Westminster System
Is policy representation in contemporary Westminster systems solely a function
of programmatic national parties, or does the election of legislators via single-member
districts result in MPs whose policy positions are individually responsive to public opin-
ion in their constituencies? We generate new measures of constituency opinion in
Britain and show that, in three different policy domains and controlling for MP party,
the observed legislative behavior of MPs is indeed responsive to constituency opinion.
The level of responsiveness is moderate, but our results do suggest a constituency-MP
policy bond that operates in addition to the well-known bond between voters and
For countries that elect their legislators using single-member dis-
tricts (SMDs), one fundamental form of substantive representation
(Pitkin 1967, 222–24) is the degree to which the policy positions of legis-
lators ref‌lect the policy preferences of their constituents—a form of
representation that has become known as dyadic representation
(Weissberg 1978, 536). To the extent that SMD elections are contested
by “responsible” (Katz and Wildenmann 1987, 7)—i.e, cohesive and
programmatic—national parties, some degree of dyadic representation is
guaranteed: If each constituency chooses between candidates based on
their party’s programme, and each legislator faithfully supports their
party’s programme, this by itself will lead to an association between con-
stituency opinion and legislator policy position (Ansolabehere, Snyder
and Stewart 2001; Miller and Stokes 1963). But does the electoral link-
age between individual legislators and their constituents created by
DOI: 10.1111/lsq.12148
C2016 The Authors Legislative Studies Quarterly published by Wiley
Periodicals, Inc. on behalf of Washington University in St. Louis
This is an open access article under the terms of the Creative Commons
Attribution License, which permits use, distribution and reproduction in any
medium, provided the original work is properly cited.
SMDs also result in within-party policy responsiveness, whereby the
policy positions of individual legislators within the same party co-vary
with opinion in their particular constituencies?
In the United States, where the vast majority of research on dyadic
representation has been conducted, the answer appears to be a qualif‌ied yes
(Ansolabehere, Snyder and Stewart 2001; Clinton 2006, 401; Kastellec,
Lax and Phillips 2010; Krimmel, Lax and Phillips 2016). Yet outside
of the United States research on dyadic representation is much less
developed (Powell 2004, 283–84). Indeed, with some rare exceptions
(Converse and Pierce, 1986), scholars have yet to empirically demon-
strate the existence of dyadic representation in many countries that
have SMD electoral systems, much less establish whether any dyadic
representation that does emerge is entirely due to responsible national
parties or at least in part due to within-party policy responsiveness.
This is unfortunate because the United States i s somewhat unusual
among SMD systems, with its relatively weak party cohesion and more
individualistic electoral competition (Bawn and Thies 2003; Carey and
Shugart 1995; Dalton, Farrell and McAllister 2011), making it an envi-
ronment particularly conducive to within-party policy responsi veness.
Westminster systems appear to present a far more challenging
environment for within-party policy responsiveness, characterized as
they are by parliamentary government with strong executive agenda-
setting powers, resulting in highly disciplined parties that compete
electorally on national policy platforms (Bawn and Thies 2003; Cox
1987). Focusing on the United Kingdom as a case study, this article asks
whether party dominance completely precludes within-party policy
responsiveness in a Westminster system, or whether, even accounting
for party, there remains some association between the policy positions
of individual Members of Parliament and policy opinion in the
constituencies they represent.
While we are not be able to establish a causal mechanism here,
even establishing the descriptive fact that such an association exists
speaks to important normative and practical debates about the merits of
Westminster systems. This is because the “strong voter-member link-
ages” purportedly fostered by SMDs in Westminster systems are
commonly highlighted by opponents of electoral reform as one of the
main reasons why the well-acknowledged costs of SMD elections—
chief‌ly, high levels of disproportionality (Carey and Hix 2011)—are
worth bearing (Norris 2001, 877).
Studies have documented evidence
that such voter-member linkages are manifest with respect to MPs’ non-
policy, constituency service-type behaviors (Cain, Ferejohn and Fiorina
1987; Norton and Wood 1993; Rush 2001; Searing 1994) and with
236 Chris Hanretty, Benjamin E. Lauderdale, and Nick Vivyan
respect to the policy issues that MPs choose to attend to (Blidook and
Kerby 2011; Soroka, Penner, and Blidook, 2009). However, research on
voter-member linkages with respect to policy positions has to date been
impeded by a lack of the required empirical measures.
Establishing the existence of within-party policy responsiveness
would also point toward a previously underappreciated channel for poli-
cy representation in Westminster systems. Kam et al. (2010) have
provided evidence that the policy positions of backbench MPs in the
Commons signif‌icantly constrain party leaders, the actors assumed to
dominate the policymaking process in Westminster systems. They spec-
ulate (301) that this inf‌luence of rank-and-f‌ile MPs could mean that
nonmarginal constituencies have more inf‌luence in the policymaking
process than previously thought (Kam et al. 2010, 201). Of course, this
only holds if it can be shown that, within a party, MPs’ policy positions
ref‌lect those of their constituents.
There are two main reasons why it has previously been so diff‌icult
to directly test for within-party policy responsiveness. First, it is expen-
sive to obtain accurate estimates of constituency policy opinion through
mass surveys. Although the per-respondent cost of opinion surveys has
decreased over time, sampling even a small number of respondents in
each of the 632 constituencies in mainland Britain quickly yields total
sample sizes in the hundreds of thousands. Second, it is diff‌icult to mea-
sure individual legislators’ policy positions. The British Representation
Study (e.g., Norris and Lovenduski 1992, 1997, 2001) has surveyed pro-
spective parliamentary candidates at many recent general elections and
asked them to indicate their position on different policy dimensions;
however, these measures suffer from low response rates (Kam et al.
2010) and cannot be linked to particular constituencies because they are
always collected on the condition that “individual replies will be treated
in the strictest conf‌idence” (Kam et al. 2010, xx). Strong party discipline
also means that differences of opinion between members of the same
party are often reconciled privately (Cowley 2002, 183; Norton 1999),
or, if they are made visible in legislative votes, are only done so in ways
incompatible with the models of sincere voting upon which many scal-
ing techniques rely (Spirling and McLean 2007).
In this article, we capitalize on recent methodological advances to
overcome these two diff‌iculties. We use methods of small-area estima-
tion to generate estimates of constituency opinion both on a general left-
right economic scale and on specif‌ic issues (same-sex marriage and the
European Union). We then show how variation in constituency opinion
is associated with within-party variation in MP positions as revealed by
scaled Early Day Motion signatures (“unobtrusive measures” of
237Dyadic Representation in a Westminster System

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