**3. Methodology**

We endeavor to verify the relationship between public attention on migration which was provided by search query in cyber space and the population migration in geographical space. Migration attention indexes (MAIs) are proposed to express public attention on migration comprehensively. Based on the different original location of migration search, we construct three MAIs as local-MAI, external-MAI, and intercity-MAI to delineate the public attention generated from local city, attention from external areas, and attention flow among urban areas; then, the correlation analysis is conducted between MAIs in cyber space and urban migrants in geographical space to further verify the aforementioned hypothesis. The framework of this paper can be illustrated in Figure 2.

Specially, the net inflow population, intercity population flow, and the floating population have been collectively adopted to depict the movement of population in this paper. The definition of migration for them can be separately clarified as follows: The net inflow population of a city is defined as population that the city has received from the external areas, which is the result of movement of people with different origins and the same destination; the intercity population flow is also defined as the movement of people, which happens among different cities; and the floating population of a city is defined under the Hukou policy of China (which has been regarded as the central mechanism underlying the unsettled nature of the floating population), of which the migration can be explained as the change in the place of personal residence.

*Int. J. Environ. Res. Public Health* **2020**, *17*, x 5 of 18

**Figure 2.** Research framework. **Figure 2.** Research framework.
