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No.71 : Public Investment and Defense Spending

Senior Economist/主任研究員 長島 直樹



  1. The conventional way of public investment has been the target of criticism in recent years. Also, there is a significant possibility that the multiplier effect, often the subject of discussion when planning economic measures, may have diminished in comparison with earlier times. Furthermore, there are certainly a lot of issues to be addressed, such as rigid budget allocation, etc. However, it is a fact that even the conventional, civil engineering-focussed public investment has contributed to private sector productivity through the formation of social infrastructure.
  2. If spending on this kind of public investment were to be reduced following a period of rapid economic growth, and these funds diverted to defense expenditure, for example, the formation of social capital would be slowed. As a result, there is every possibility that productivity growth would stagnate, causing a slowdown in the economic growth. This effect is not noticeable in the short term, but would become markedly noticeable over a longer term of 20 to 30 years.
  3. An estimate of the productivity effect of social capital shows that between 1970 and 1997, on average, 'an increase of 1% in the social capital leads to an increase of 0.2% in the productivity of private capital.' Based on the assumption that approximately 60% of public investment contributes to the formation of new social capital, we estimated what would be the effect on GDP if a certain portion of public investment were to be diverted to defense spending.
  4. If we were to hypothesise that, since 1970, Japan's defense spending has been 2% of GDP, rather than 1%, then the social capital for 1997 would be 58 trillion yen (15%) less than the actual figure, and the actual GDP would be lowered by between 3.1 and 5.5%. It has to be acknowledged that the impact of the 'peace dividend' has been substantial.
  5. China's current military spending is estimated to be around 5% of GDP. If this were reduced by even 1%, and that portion diverted to the provision of social infrastructure, potentially substantial long term benefits can be imagined. Such a reduction in military spending would surely be beneficial to China's own economic development.


  1. 従来型の公共投資は近年、非難の的になっている。景気対策の際に話題になる乗数効果も以前よりは薄れている可能性が高い上、硬直的な予算配分など問題は確かに多い。ただ土木中心の従来型公共投資も、社会資本の形成を通じて民間部門の生産性向上に寄与してきたことは事実である。
  2. 高度成長期以降、このような公共投資を減額し、その分が例えば防衛費支出に消えていたとすれば社会資本の形成は遅れていた。結果的に生産性上昇率の低下を通じて成長率も伸び悩んでいた可能性がある。この効果は短期間には現れないが、20~30年といった長期間続くと顕著になる。
  3. 社会資本の生産力効果を推計すると、1970~1997年平均で「社会資本が1%増加すると民間資本の生産性は0.2%上昇する」という結果になる。公共投資の約6割が新たな社会資本形成に寄与する想定のもとで、公共投資の一部が防衛費に消失していたとする想定ケースをGDPベースで試算してみた。
  4. 1970年以降、日本の防衛費がGDP比約1%ではなく2%で推移したと仮定すると、97年の社会資本は実際よりも58兆円(15%)圧縮され、実質GDPは3.1~5.5%低下していたことになる。「平和の配当」は大きかったと言わざるを得ない。
  5. 中国は現在GDP比約5%の軍事費支出を行なっていると言われるが、もし1%でも圧縮し、社会インフラの整備に回せば、その中長期的な効果は大きいことが想像される。中国の軍縮は中国自身の経済発展にとっても好ましいことではなかろうか。


Public Investment and Defense Spending [123 KB]