1. Ozawa led a group that voted against the DPJ's proposed consumption tax increase. In response, the DPJ expelled Ozawa and his followers in the vote, and Ozawa and his group resigned from the DPJ nearly simultaneously.
2. The effective number of parties index is calculated by squaring the proportion of the vote or seat shares of each party, and then dividing 1 by the sum of all the squares: Nv = 1/$SG(vi 2) or Ns = 1/$SG(si 2)
3. In 2009, Komeito won twenty-one PR seats and no SMDs. The SDPJ won four PR seats and three SMDs. The JCP won nine PR seats and no SMDs. Your Party won three PR seats and two SMDs.
4. In the United States, it is striking that two of the highest-profile party switches in recent years—the cases of Joseph Lieberman and Arlen Specter—in the Senate occurred when the incumbents faced difficulty gaining their party's nomination.
5. Another type of possible contamination effect comes from the House of Councillors (HC), where the more permissive rules (high district magnitude national PR races and multimember district SNTV for each prefecture) have helped small parties remain afloat. It is conceivable that the existence of these parties in the HC has allowed some to continue to contest House of Representatives races.