Public research and development

 
Public research and development (Public R&D) refers to the R&D activities related to public sectors, including governments, colleges and non-profit organizations. Public R&D include academic fundamental research, applied research and R&D grants and contracts to private sectors, where later two are known as 'R&D subsidy'. Public R&D could be understood as a funder or a performer of an R&D activity. According to National Science Foundation in U.S., in 2015, R&D expenditures performed by federal governments, local governments, colleges and non-profit organizations are 54, 0.6, 64, and 20 billions of dollars, respectively. Meanwhile, industries perform R&D expenditures of 356 billion dollars. Moreover, R&D expenditures funded by federal governments, local governments, colleges and non-profit organizations are 121, 4.3, 17, and 19 billions of dollars, respectively. R&D expenditures funded by industries are 333 billion dollars. In terms of R&D funders, public R&D to private R&D ratio is about 0.5. 
Economic impacts.
Economists have made significant strides to understand the dynamics of public R&D, along with its cascading effects.
Productivity.
Scholars generally propose that public R&D enhances industrial productivity (e.g., Levy and Terleckyj, 1983; Nadiri and Mamuneas, 1994).However, the improvement of productivity could result in R&D spill-over of public sectors, researcher movements and co-operation between public and private sectors. 
R&D investment of private sectors.
Economists are particularly concerned about whether public R&D stimulates or crowds out the private sector R&D. It is generally known as a 'policy success', if the public R&D (especially the government R&D subsidy) could stimulate the R&D investment of private sectors. So far, there is no conclusive viewpoint in the literature (e.g., Toole, 2007 ;Cohen, Coval, and Malloy, 2011; Azoulay, Zivin, Li, and Sampat, 2018). 
Stock returns.
Public R&D is also positively related to stock returns of industrial firms (Chen, Chen, Liang, and Wang, 2020). Although they show that abnormal returns based on public R&D ratio generate about 0.9% abnormal returns per month, and suggest that the positive relation could be interpreted by increased cash flow risks.
References.
/ref>; Nadiri and Mamuneas, 1994