連合政権の安定性と政党システムの理論

抄録

As Maurice Duverger pointed out, proportional representation tends to lead to the formation of many independent parties. Traditionally, analysis of the consequences of electoral systems and party systems has focused upon two central topics: the influence of the electoral system upon the number of effective parties, and its effects upon the political stability of a country. Political stability in this context means ‘cabinet durability.’
In Western Europe, many countries have been governed by coalition governments. And they have experienced stable government. In Japan, however, there are many misconceptions about coalition government, namely that coalition government is unstable. It is not the case in European politics. Consequently, this paper aims at discussing the relations in terms of the ‘durability of coalition government and party systems.’
Michael Laver and Norman Shofield analyzed government duration and the effective number of parties, by country, from 1945 to 1987. In their comparative study of coalition governments, coalition stability varies very considerably from regime to regime. It seems that cabinet duration is more likely to rise than to fall when the size of the party system increases. While the size of the party systems in Finland, Luxenburg, and Iceland went up between the periods from 1945-71 and from 1971-87, cabinet stability also rose. Only in the interesting cases of Belgium, Sweden, and Denmark we see clear evidence of the Japanese misunderstanding about the relation between cabinet stability and the size of the party system.
Nevertheless, in terms of the study of ‘coalition government, ’ there is at present, no systematically arranged condition. What relationship do party systems have to government stability? As the coalition is formed and is stabilized, what type of cabinet emerges, and in what country can we see that type? What are the relationship between social cleavages, left-right ideology and coalition government? Social cleavages and left-right ideology often determine party systems. In real world politics, what type of coalition is most frequently formed, and how long does it remain stable? It seems that by synthesizing various theories, it will become possible to understand the answers to these questions.
Turning our attention to the Japanese case, it seems that the past research has concentrated on the formation of coalition government rather than on its stability. In that sense, it is necessary now to discuss coalition theories in terms of cabinet stability.
We try to answer the question as to why some cabinets last longer than others, any why cabinets in some countries tend to last longer than those in other countries. In general, one-party cabinets are said to be more durable than coalition cabinets, minimal winning cabinets are said to be more durable than oversized ones. and cabinets in systems with two or relatively few parties are said to be more durable than cabinets in multiparty systems.
Thus, we have briefly viewed the stability of coalition government and party systems. However, we must consider further the problem of public policy. If the stability of coalition relates to the stability of party system, it is necessary to maintain a coalition government by havig it correspond to people's demands and absorb people's support. Effective public policy is a useful means for achieving this end.
What policy will be offered? When? And what combination will be formed? Given this potential importance of public policy, it seems that we must pay attention to the relationship between individual political parties and public policies.