## 5 Interaction between Planning Research Investment Intensity and Urbanization  
### Time Feature of Planning Research Investment Intensity and Urbanization  
The interactive relationship between planning research investment intensity and urbanization was studied based on quantitative data. It is country-level research taking the country as case studies, and the research time is selected as year of 2019. In this research, 'planning research investment intensity' is defined as the amount of planning research literature per capita (per million population) in the selected country. The urbanization refers as the urbanization rate of selected countries. Therefore, by comparing the urbanization rate and 'planning research investment intensity' of countries in 2019, the interactive feature between the two is studied. The urbanization rate and literature per capita of countries are plotted in the form of a scatter plot, in which the horizontal axis is the urbanization rate and the vertical axis is the literature per capita, which represents the investment intensity of planning research. Through the scatter diagram, a pattern can be found visually and these countries could be divided into two types of development pattern, namely, (1) countries whose urbanization rate increased while their planning research investment intensity does not increase, and (2) countries for with both urbanization rate and planning research investment intensity increased. Further in-depth analysis will be conducted in this study. In theory, urbanization is a long and dynamic development process from low urbanization rate to high over time. It is assumed that the urbanization rate of all countries will grow with the development [14]. Therefore, from the perspective of dynamic development of urbanization, the dynamic relationship between planning research investment and urbanization is studied, and a relatively obvious time feature is found. From a dynamic perspective, this paper analyzes the characteristics of the relationship between planning research investment and urbanization in various countries, and presents them in a scatter plot, which can be analyzed and summarized into 6 six different categories, represented by A, B, C, Cl, D, and D1 (Figure 3). The relationship between planning research investment and urbanization can be generally summarized into following categories. **Category A: pre-urban societies with very little investment**  
Before the urbanization rate reaches 50%, the intensity of planning research is very low, and countries seldom pay attention to it. Before urbanization rate reaches 50%, only two countries in the 47 countries carried out the research outcome, with very low per capita (0.9 to 1.6 per one million people), which proves that when the urbanization rate is lower than 50%, major countries were unlikely to invest in planning research, largely because in the low stage of urbanization rate, there were fewer urban problems. In another view, in the early stage of urbanization, planning was mainly based on practice, and the research on planning was not the mainstream, thus a complete research eco-system had not established. **Category B: began to accelerate when urbanization past 50%**  
Based on data, the investment of planning research began to grow after the urbanization rate exceeds 50%, when urban problems soaring in this stage of urbanization, as many relevant studies have also proved the correlation between the stage of urbanization and urban problems. It is not until the urbanization rate exceeds 50% that urban problems erupt, leading to a surge in relevant research as the basis for solving urban problems [36]. This is related to the theory of 'intelligent urbanization' put forward by scholars [37]. **Category C: high urbanization but low investment**  
When the urbanization rate reaches 60-80%, a large number of planning studies begin to appear in this stage, while their per capita number is low.