The Convergence Coefficient across Political Systems
Table 7
Convergence and fragmentation.
Plurality systems
Variable
US
Britain
Political system
Presidential
Parliamentary
Election year
2000
2004
2008
2005
2010
Conv. Coef.a (conf. Int.b)
0.38 (0.2, 0.7)
0.45 (0.2, 0.8)
1.11 (0.7, 1.5)
0.84 (0.5, 1.3)
0.95 (0.9, 1.1)
Converge to mean
Yes
Yes
Yes
Yes
Yes
Number of partiesc
2
2
2
9
9
President
env
c
2.16
2.05
2.05
House of Representatives
House of Commons
env
d
2.25
2.18
2.18
3.61
3.74
ens
d
2.02
2.00
2.00
2.47
2.58
Proportional Representation
Israel
Turkey
Poland
Political system
Fragmented
Fragmented
Cut off
Fragmented
Election year
1996
1999
2002
1997
Conv. Coef.a (conf. Int.b)
3.98 (3.5, 4.6)
1.49 (0.7, 2.2)
5.94 (4.4, 7.4)
6.82 (5.8, 7.8)
Converge to mean
No
Likely
No
No
Number of partiesb
11
9
10
7
Prime Ministerse
env
c
2.00
Knesset
Parliament
Sejm
env
c
5.84
6.91
5.62
4.99
ens
c
5.89
6.35
2.29
6.77
Anocracies—plurality
Georgia
Russia
Azerbaijan
Political system
Presidential
Presidential
Presidential
Election year
2008
2007
2010
Conv. Coef.a (conf. Int.b)
2.42 (2.0, 2.9)
1.83 (1.4, 2.3)
1.44 (0.1, 3.0)
Converge to mean
No
Likely
No
President
President (2008)
President (2008)
Number of partiesc
8
4
7
env
d
2.76
1.88
1.31
Parliamentary
Duma (2007)
National assembly (2010)
Number of partiesa
5
7
12
env
d
2.56
2.22
4.74
ens
d
1.55
1.94
2.27
This is the central estimate of the convergence coefficient.
bConf. Int.: confidence interval rounded to the nearest tenth.
cNumber of parties who won votes in the election.
dBased on the number of parties who obtained seats in the election.
eThis was the first time the Prime Minister was elected on a ballot separate from the Knesset.
