Coalition governments are common in Japan not because the parties involved agree on everything, but because working together can give them enough seats to govern more securely.
However, coalition government has not always been the norm in Japan. For much of the postwar period, politics was dominated by the Liberal Democratic Party. A major turning point came in 1993, when the LDP lost power and a coalition government led by Morihiro Hosokawa was formed.
To understand why coalitions matter, the first thing to look at is the House of Representatives.
Japan has a parliamentary system, so if one party does not hold enough seats on its own, joining with another party can make the government more stable.
Elections to the House of Representatives use both single-member districts and proportional representation. This system is not itself the reason coalition governments exist, but it is one factor that allows several parties to maintain representation in the Diet.
Japan also has the House of Councillors.
A government may hold a majority in the House of Representatives without holding one in the House of Councillors. Ordinary legislation generally needs approval from both chambers. If the House of Councillors rejects a bill, the House of Representatives can override that decision only with a two-thirds majority of members present.
For that reason, having a coalition partner that can also provide support in the House of Councillors can be extremely important.
Parties in a coalition do not necessarily agree on every policy. They cooperate on areas where they can reach agreement and negotiate over areas where they differ. A coalition is therefore less a group of parties with identical ideas than a practical arrangement for governing.
But coalitions also create an interesting paradox.
Even a relatively small party can gain considerable bargaining power if the government would lose its majority without it. As a result, the views of a smaller coalition partner can sometimes influence policy more strongly than its number of seats might suggest.
Some people may see this as giving a small party too much influence. Others may see it as a way of ensuring that voters who supported smaller parties also have a voice in government.
So coalition governments appear repeatedly in Japan not because Japanese voters naturally prefer coalitions. They are a practical result of parliamentary arithmetic: a single party may not have enough seats on its own, and support in both houses can matter for governing effectively.
References
- House of Representatives, “Composition of the Diet”
- House of Representatives, “Powers of the Diet”
- National Diet Library, “Formation of the 1955 System”
- Prime Minister’s Office of Japan, “79th Prime Minister Morihiro Hosokawa”
