## 2 Literature Review
### Innovation Factors for Technological Development  
Though the features of innovative entities such as firm size, ownerships, and R&D investment are viewed as significant for technological breakthrough [51], this is not the sole factor in a complex city. Factors such as economic strength and dynamism, talents and their mobility, urban construction level, etc., are also tested as influential [10; 52]. Dating back to early 20 th century, the correlation between economic performance and technological advancement was evident [53]. Technological progress, in whatever fields, would bring about visible economic growth, and a better economy would assuredly reinforce technological advancement [54]. Recently, however, with the increasing complexity of economic innovative activities, the bundle relation between economy and innovation is not as certain as usual in some areas. For instance, in a study about China's green growth, technological innovation was found as having a positive impact, but GDP was not [55]; in the Chinese video game industry, applying technologies to military training, biomimicry, and product presentation is considered far more significant than its mere economic contributions [56]. Is the economy still overridingly associated with innovation in a city-region? This research employs GDP, GDP per capita, and public expense to represent the economy from three aspects: in particular, GDP represents economic aggregates, GDP per capita represents economic efficiency per person, and public expense presents economic inputs for social development. The resident population serves as the talent pool and the primary source of human capital for innovative activities [57]. Yet, quality innovative outputs shall depend on quality talents who normally engage in intellectual intensive work. University students in this research provide as a quality talent pool for venture activities [58]. Cities are the font of economic innovation [13; 59] and its built environment matters for innovation productivity [10; 60]. To identify how innovative outputs are associated with the built environment, this research employs building construction, green area per capita, and road mileage for analysis: the building construction represents architectural environment, green area per capita represents public space environment, and road mileage represents the transportation environment. For developing countries, gaining innovation capacity may also depend on foreign sources of knowledge and technology which possibly flow through a variety of channels such as FDI [61]. For instance, by importing the licensing of technology and forming alliances with firms of developed countries, Japan fast caught up with advanced foreign technology in the postwar phase [62]. However, the importance of FDI as a channel for knowledge transfer varies from place to place, e.g., South Korea and Taiwan and its role in technological innovation, thus is at best being discussed case-by-case. Given the review above, the following research questions are proposed:  
RQ3. How do the cross-classified technologies associate with urban innovation factors? Is economic performance overriding other factors such as human capital, urban built environment, and foreign resources for technological innovation, as evidenced in the YRD?