*5.2. The Effect of City Cluster Policy on CO2 Emissions across City Cluster Positioning Level*

The level of the city cluster positioning determines the resource allocation capacity of the city cluster. The city cluster with a high positioning level can provide favorable organizational leadership and abundant human, financial, and other resources, which support the implementation of the city cluster to reduce city carbon emissions. However, the regional-level city cluster governments have a limited ability to allocate resources. In this case, they cannot provide appropriate policies and funds to attract talents and promote the transformation and upgrading of enterprises. The world-level city cluster also does not affect the reduction of carbon emissions. The reason is that the goal of the world-class city cluster is to create a more open Chinese market, and attracting foreign investment is the top priority. As a result, the policy benefits of regional and world-level city cluster cannot be realized. The national-level city cluster has sufficient allocation capacity to reduce carbon emissions.

The result is shown in column (1) of Table 7. Only variable Nation\*Treat\*Post is significantly negative with LnCO2, the regional and world city cluster positioning show weak policy effects, neither variables World\*Treat\*Post nor Region\*Treat\*Post are significantly affected.


**Table 7.** The effect of city cluster policy on CO2 emissions across city cluster positioning level.

Note: *t* statistics are shown in parentheses; \*\*\* represent significance at the 1% levels, respectively.
