Major factors affecting China's inter-regional research collaboration: Regional scientific productivity and geographical proximity

On the basis of the measured frequency distribution of China's inter-regional co-authored papers covered by the Chinese Science Citation Database, this paper shows the pattern of China's inter-regional research collaboration (IRRC), and analyzes how the collaborative pattern was formed. A new method is used to calculate the expected value matrix based on an observed value matrix of IRRC, which is asymmetric and has no diagonal elements. The results fall into three groups. 1) Regional scientific productivity affects both the collaborative preference and ranking of authors' name; 2) geographical proximity is an important factor determining the pattern of IRRC; 3) when using Salton's measure, regional mean collaborative strength increases as the regional productivity increases, and as the distance between two regions decreases.