This paper defines the macro-investment efficiency as the sensitivity of the regional investment rate to the return on capital measured by the prefecture-level city as a unit. On the basis of measuring the change trend of China's macro investment efficiency according to this definition, this article mainly focuses on the impact of the expansion of government investment on the efficiency of macro investment. The article first estimated the investment rate and return on capital of 179 prefecture-level cities in China from 2006 to 2013, and found that after 2009, while the investment rate of prefecture-level cities rose sharply, the return on capital dropped significantly. The econometric test found that, on the whole, China's capital flowed to areas with high capital returns, but after 2009, the positive correlation between the investment rate and the return on capital dropped significantly, indicating that the guiding role of capital return rate on capital flow is greatly reduced, and the efficiency of macro investment has deteriorated significantly. A further measurement test found that the larger the scale of local financing platform debt, the stronger the negative correlation between the investment rate and the return on capital. That is, the lower the macro investment efficiency, the greater the negative impact of the debt scale of the local financing platform on the macro investment efficiency, which mainly appeared after 2009. Because the scale of local financing platforms can better measure the scale of local government investment, the results can show that the expansion of local government investment scale after 2009 has had a negative impact on the efficiency of macro investment.
