中文摘要：

文章在一个具有Marshall-Arrow-Romer知识外部性的四部门经济中，通过研究代表性家庭的动态最优化问题，考察了人力资本投资、研究开发和经济可持续增长之间的内在关系以及相应的政策含义问题，得出的主要结论是：1.人力资本的积累效率和知识外部性的大小会影响经济稳态增长率的高低；2．主观时间偏好率越大、边际效用弹性参数越小的国家稳态增长率越低；经济中技术创新率的提高和教育部门生产效率的改进会提高一国的稳态增长率，反之则反是；3．知识的外部性越大，最终产品部门的产出和研究开发部门的知识增量越高，稳态的经济增长率越高，反之则越低；4．政府应该建立、健全和完善尊重知识产权、激励创新的政策环境，以引导经济达到可持续的稳定增长状态。文章运用1978--2006年的时间序列数据进行实证研究，命题的主要结论得到了经验证据的支撑；同时，也发现了一些不同于已有命题的现象。

英文摘要：

In a four-sector economy with Marshall-Arrow-Romer knowl- edge externalities, the paper studies the relationships among human capital investment, R＆D and sustainable economic growth as well as the related policy implications through the analysis of dynamic optimization of representative families. The main conclusions are as follows： Firstly, the accumulation efficiency of human capital and the knowledge externalities will affect the steady-state growth rate of the balanced economic growth path; Secondly, a country with larger subjective time preference and smaller marginal utility elasticity parameter has a lower steady-state growth rate, and the improvement of technical innovation rate and education sector＇s productivity will increase the steady-state growth rate, and vice versa; Thirdly, the greater the knowledge externalities are, the more the output of final output sector, the knowledge increment of R＆D sector will be and the higher the steady-state economic growth rate will be, and vice versa; Fourthly, the governments should create and perfect a policy environment which pays more attention to knowledge property protection and innovation incentives, in order to lead the economy to a steady state with sustainable growth. The paper makes an empirical study by employing time series data from 1978 to 2006. The empirical evidence supports a majority of propositions. Meanwhile, the study also demonstrates some contradictions with our propositions.