Median Voters, 1950-1995
Codebook
August 2002 Version
Michael D. McDonald
Department of Political Science
Binghamton University (SUNY)
Binghamton, NY 13902-6000
UNITED STATES
mdmcd@binghamton.edu
Acknowledgements. Many of the data entries in this file are derived from data collected and input in a
collaborative effort with Silvia M. Mendes and Aida Paskeviciute.
1
Data Set Description
The data report estimated left-right locations of median voters of 21 countries at each constitutionallybased election from 1950 through 1995. For each country and election, there are six estimated median
voter positions. The six variations arise from differences with respect to two assumptions: (1) the
left-right position of parties at the time of an election, and (2) the distribution of voters who are to the
left of the left-most party or to the right of the right-most party. Cases are ordered by (1) country, (2)
basis of median voter assumption, (3) election.
In addition to reporting the estimated median voter positions, the data report information used to create
the estimates. The formula can be found in most introductory statistics textbooks under a heading such
as ‘computing a median from grouped data.’ HeeMin Kim and Richard Fording have applied the
grouped median formula to party position data and party vote percentage data and, in that context,
present it as:
M = L + {(50 - C)/F} * W.
where
M = Median voter position
L = The lower end (left-right score) of the interval containing the median
C = The cumulative vote share up to but not including the interval containing the median
F = The vote share in the interval containing the median
W = The width of the interval containing the median—i.e., the range of midpoints
between the party of the median voter and adjacent parties to its left and right
See:
Kim, HeeMin and Richard Fording. 1998. “Voter Ideology in Western Democracies, 1946-1989.”
European Journal of Political Research 33:73-97.
Number of Cases
N = 1614
There were 269 elections in these 21 countries. Given six estimates of a median voter’s position per
election, the number of cases is 1620 (i.e., 269 x 6).
The three elections reported here but not included in the associated Governments data file are two
from the French Fourth Republic and the December 1995 Austrian election that did not produce a
government until March 1996.
Accuracy Status as of August 2002
The data have been checked only once after input. Contact McDonald by e-mail, if you suspect that
an entry is in error.
2
Sources
We rely on five sources. These are identified here. In the Variable List below, we identify the source
of each variable by a short title provided in parentheses following the source citation. Variables that
are either created or computed as logical or arithmetic derivations of other data are also identified as
such.
Budge, Ian Hans-Dieter Klingemann, Andrea Volkens, Eric Tannenbaum, and Judith Bara. 2001.
Mapping Policy Preferences: Estimates for Parties, Electors, and Governments 1945-1998.
Oxford: Oxford University Press. (source = CMP98)
European Journal of Political Research, annual country political updates (source = EJPR).
Mackie, Thomas T. and Richard Rose. 1991. International Almanac of Electoral History, 3rd ed.
Washington: Congressional Quarterly, Inc. (source = MR)
Volkens, Andrea, Kai-Uwe Schnapp, and Jürgen Lass. 1992. Data Handbook on Election Results and
Seats in the National Parliaments of 26 Contemporary Democracies, 1945-1990. Berlin:
WZB. (source = Volkens et al.)
Woldendorp, Jaap, Hans Keman, and Ian Budge. 2000. Party Government in 48 Democracies (19451998). Amsterdam: Kluwer Academic. (source = WKB)
3
VARIABLE LISTING
Var #1
NATION:
Country name (source = created)
Var #2
NATIONID:
Country numeric code (source = CMP)
Var #3
MVBASIS:
Basis of median voter calculation (source = created)
Var #4
ELECDATE: Election date (source = Volkens et al, MR, & EJPR)
Var #5
TOTALPCT: Vote percentages of parties for which there are CMP data
(source = Volkens et al, MR, & EJPR)
Var #6
MDNLEVEL: Vote percentage to identify the median voter, given that only
parties for which CMP data are available are used in the
calculation (source: computed)
Var #7
VOTELEFT: Cumulative vote percentage of the parties to the left of the party
supported by the median voter (sources: alignment = CMP; vote% =
Volkens et al, MR, & EJPR)
Var #8
MPVPCT:
Vote percentage of the party supported by the median voter
(source = Volkens et al, MR, & EJPR)
Var #9
LEFT:
Position of the party adjacent and to the left of the median
(source = CMP)
Var #10
MEDNPTY:
Position of the party supported by the median voter
(source = CMP)
Var #11
RIGHT:
Position of the party adjacent and to the right of the median
(source =CMP)
Var #12
C:
The cumulative vote share up to but not including the interval
containing the median (source = computed)
Var #13
F:
Vote share in the interval containing the median
(source = computed)
Var #14
MIDLEFT:
Midpoint between party in median position and party in the
adjacent position to the left (source = computed)
Var #15
MIDRIGHT: Midpoint between party in median position and party in the
adjacent position to the right (source = computed)
Var #16
W:
Width of interval containing median (source = computed)
Var #14
ADD:
Term added to lower end of interval (source = computed)
Var #15
MDNVOTR: Median voter left-right position (source = computed)
4
VARIABLE DESCRIPTIONS
Var #1
NATION:
Country name
Australia
Austria
Belgium
Canada
Denmark
Finland
France
Var #2
NATION:
11
12
13
14
15
21
22
Var #3
2
3
4
5
6
Norway
Portugal
Spain
Sweden
Switzerland
United Kingdom
United States
Country numeric code
Sweden
Norway
Denmark
Finland
Iceland
Belgium
Netherlands
MVBASIS:
1
Germany
Iceland
Ireland
Italy
Luxembourg
Netherlands
New Zealand
23
31
32
33
35
41
42
Luxembourg
France
Italy
Spain
Portugal
Germany
Austria
43
51
53
61
62
63
64
Switzerland
United Kingdom
Ireland
United States
Canada
Australia
New Zealand
Median voter basis
Uses election-specific party position and Kim-Fording assumption about the
distribution of voters
Uses three-election moving average party position and Kim-Fording assumption
about the distribution of voters
Uses post-war average party position and Kim-Fording assumption about the
distribution of voters
Uses election-specific party position and adjusted Kim-Fording assumption about
the distribution of voters
Uses three-election moving average party position and adjusted Kim-Fording
assumption about the distribution of voters
Uses post-war average party position and adjusted Kim-Fording assumption about
the distribution of voters
Note: the election-specific, three-election moving average, and post-war average
indicators of party positions are described in the Parliaments and Governments data
set under the variables ELECL_R, MA3L_R, and PTYXL_R.
Voter distributions under codes 4, 5, & 6 are assumed to be different from those
assumed by Kim and Fording. When the farthest left or farthest right party in a
system is involved in the formula, Kim and Fording allow the extreme score of –100
or +100 to mark the endpoint where voters of that party are located. Rather than
assuming the party’s voters are so widely dispersed, this variable assumes they are
spread in a symmetrical interval around the party’s position. For example, for a
leftmost party at –15 and a 0 midpoint between it and an adjacent party on the right,
we assume the left boundary of that party’s voters is –30.
5
Var #4
ELECDATE: Election date
Year and month of election (e.g., 5001 is January 1950)
Var #5
TOTALPCT: Vote percentages of parties for which there are CMP data
The median voter calculations reported here require that parties be aligned from left to
right. Thus, only parties that have CMP left-right scores are involved in the
calculations. This variable is used to re-proportionalize vote percentages with respect
to parties with left-right scores.
Var #6
MDNLEVEL: Vote percentage to identify the median voter, given that only
parties for which CMP data are available are used in the
calculation
Computed as TOTALPCT divided by 2
Var #7
VOTELEFT: Cumulative vote percentage of the parties to the left of the party
supported by the median voter
Vote percentage of all parties to the left of the party supported by the median voter
Var #8
MPVPCT:
Vote percentage of the party supported by the median voter
Vote percentage of the party supported by the median voter
Var #9
LEFT:
Position of the party adjacent and to the left of the median
Left-right position of the party adjacent and to the left of the party supported by the
median voter
Var #10
MEDNPTY:
Position of the party supported by the median voter
Left-right position of the party supported by the median voter
Var #11
RIGHT:
Position of the party adjacent and to the right of the median
Left-right position of the party adjacent and to the right of the party supported by the
median voter
Var #12
C:
The cumulative vote share up to but not including the interval
containing the median
Computed as [(VOTELEFT / TOTALPCT) * 100)
6
Var #13
F:
Vote share in the interval containing the median
Computed as [(MPVPCT / TOTALPCT) * 100)
Var #14
MIDLEFT:
Midpoint between party in median position and party in the
adjacent position to the left
Computed as [(LEFT + MEDIAN) / 2]
Var #15
MIDRIGHT: Midpoint between party in median position and party in the
adjacent position to the right
Computed as [(RIGHT + MEDIAN) / 2]
Var #16
W:
Width of interval containing median
Computed as MIDRIGHT - MIDLEFT
Var #17
ADD:
Term added to lower end of interval
Computed as {(50 - C)/F} * W
Var #18
MDNVOTR: Median voter left-right position
Computed as LEFT plus ADD