Party Move and the Median Voter Theorem 1  Definition of the median voter theorem = Political parties will pursue policies that appeal most to the median voter. = It explains why political parties often promote the similar policies ( 예 : 복지정책 ) to appeal to independent (moderate) voters  One big condition is about the ideological distribution of voters.  The theorem works if voters’ ideological distribution is a normal distribution (bell-shaped).  What happens if voters’ ideological distribution is bimodal?

Spatial Competition and the “Power of the Median Voter” Voting in a Congressional Committee over Two Minimum Wage Proposals, X and Y Five Senators A, B, C, D, and E and their minimum wage level preferences as follows Senator A: the minimum wage should be abolished. Senator B: $2.00 per hour Senator C: $5.50 per hour Senator D: $6.50 per hour Senator E: $10 per hour (the highest level) 2

Five senators on the committee and their minimum wage level preferences 3

The Power of the Median Voter 1) If senators choose between the two minimum wage proposals, X ($3.50) and Y($7.00), which proposal will prevail in this committee, X or Y? Senators A, B prefer X vs. Senators C, D, E prefer Y  3-2 majority decision in favor of proposal Y 4

The Power of the Median Voter 2) Suppose it was possible to make amendments and option X was changed into $5.00/hr, leaving Y unchanged. Then, which proposal will be chosen, X or Y? This time, senators A, B, C prefer X vs. senators D, E prefer Y  3-2 decision in favor of proposal X 5

The Power of the Median Voter 3) Allow one more amendment and this time moving Y precisely to Sen. C’s ideal minimum wage ($5.50), then, what happens? 3-2 (C, D, E vs. A, B) majority favors proposal Y. 6

The Power of the Median Voter Then, no other amendment to X would allow it to unambiguously defeat proposal Y. The best thing supporters of proposal X could hope to do would be to amend it so that X, too, perfectly correspond to Sen. C’s position. In conclusion, the motions in this example tend to converge on Sen. C’s ideal minimum wage level. By the way, who is Senator C? Senator C is the median member (voter) of the committee.  The Power of the Median Voter 7

Who in 2009 was going to be a critical member of the Senate during the first year of the Obama presidency?  한국 대통령과 정당정치에 적용 가능성 ? If Not, Why Not? Woon (April 2009, 331): Predicting policy change in the Obama presidency 8

Party Position vs. My Position Mean & Standard Deviation When a voter is deciding her electoral choice, both party position & party unity (split) matter.  (Average) Party position is represented by mean.  Party unity(split) is represented by standard deviation. 9

Party Position vs. Party Split  If the Democratic Party’s policy position is closer to the voter’s ideal policy position, the voter will vote Democratic.  What if, however, Democrats are too much divided?  Then, it is possible that this voter would end up voting Republican, instead. 10

Hinich and Munger (1997, 125)

Mean and Standard Deviation: (Ex) Party Position and Voters’ Choice  Voter i’s ideal policy position:  Party’s average policy position:  Mean  Party’s split:  Standard Deviation 12

Mean vs. Standard Deviation: (Ex) Party Position and Voters’ Choice Then, voter i will vote for Republican Party. BECAUSE, 1) The smaller the difference between voter’s position and party’s position, the better. 2) The smaller the party split, the better. 3) With both party position and split taken into account, vote i will vote for R, when the condition above is met. 13

If  If we partially use the formula to only consider the difference between this voter and mean party position, then  Which party shows a smaller distance with voter i’s position?  It is D (4), not R (16)  So, will this voter vote for the Democratic Party, whose average policy position is closer to his or hers? 14

Wait a minute!!! We also have to consider party split as well as party average position. Now, let’s use the full formula to consider party split as well. As for the Republican Party, As for the Democratic Party, Now, after taking party split (sd) into account, which party is a better fit to this voter?  It is the Republican Party! (18), not the Democratic Party (20) 15

Mean and SD for party politics  In short, this voter will vote for Republican Party after considering not only party position (mean) but also party split (standard deviation).  Conclusion: “In spite of party position (mean) being close to a voter’s preference, the voter could end up supporting the rival party, due to party split (standard deviation).”  Again, party labels offer a shorthand cue that keeps voting decisions cheap and simple, if and only if the labels are fully informative.  A high level of division  a high level of uncertainty  then, party labels are not necessarily informative 16

Which Party System do you prefer?  Party Polarization ( 정당양극화 )  No room for negotiation  What about “Responsible Party System”?  Ready to compromise  No difference between the parties  What about “Third Party or 안철수 현상 ”? 17