median_voter(positions, voteshares = "pervote", scale = "rile",
groups = c("country", "edate"), ...)median_voter_single(positions, voteshares, adjusted = FALSE,
scalemin = -100, scalemax = 100)
median_voter) a data.frame containing a column as
named in argument scale (default: rile) and one as named in argument voteshares (default: pervote);median_voter) the name of a column in the data.frame
positions that contains the vote sharesmedian_voter_singlemedian_voter is able to compute the median voter positions for multiple
elections at once, while median_voter_single treats data as coming from
a single election.calculated according to the formula by Kim and Fording (1998; 2003)
$$m = L + \frac{K-C}{F} W$$
Where m is the median voter position, L is lower end of the interval containing the median, K is 0.5*sum(voteshare), C is the cumulative vote share up to but not including the interval containing the median, F is the vote share in the interval containing the median and W is the width of the interval containing the median.
Different parties with the same left-right position (e.g. alliances) are treated as one party with the cumulative vote share.
In the adjusted formula the midpoint is "mirrored" from the midpoint of the other side: "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." (McDonald 2002)
Kim, Heemin and Richard C. Fording (2003). "Voter ideology in Western democracies: An update". In: European Journal of Political Research 42.1, 95-105.
McDonald, Michael D. (2002). Median Voters: 1950-1995. url: www2.binghamton.edu/political-science/research/MedianVoter.doc