## **5.2. Robustness Tests**

Several sensitivities are performed to test the robustness of our results. Because transport corridors are often conceived to connect large urban centers (booming centers of economic activity), excluding these end points limits the analysis to the areas along the corridor that were likely connected more arbitrarily (randomly). Columns 3 and 4 in tables 2 and 3 report the estimation results when 20 percent of the corridor area at the end nodes of the transport corridor is excluded. Moreover, it could be that some corridors are not envisioned to connect cities that happen to be at the ends of the corridor, but rather several cities, some of which are located at the ends of the corridor and some along the corridor alignment. To account for this possibility, the human settlement data prior to the start of project were used to exclude built-up urban centers. These results are reported in columns 5 and 6 in tables 2 and 3. The results across the various sensitivities are largely consistent, with a few exceptions. First, the robustness results hint that trade openness at appraisal could have a positive impact on local economic activity in non-nodal areas (column 3), and the impact of general policy reforms in non-nodal areas could also be positive (column 4). Second, the robustness results hint that a larger connectivity increase could negatively influence local economic activity (table 3, column 4), once again hinting at the need to balance ambition in project scope with the accompanying operational complexity. These nuances in the results could warrant future research.

# **6. Conclusion**

This paper conducted a survey of large transport infrastructure (corridor) projects supported by the ADB, JICA, and World Bank. It used the survey data to catalog the project characteristics and relate them to success measures, focusing on a WEB—local economic activity. To this end, the paper used the differencein-differences methodology, conditioning on country context, project design and implementation, and complementary policies and institutions. The underlying multivariate meta-regressions thus linked project characteristics to local economic activity measured through geocoded data on nightlights intensity.

The analysis found that some initial conditions and project characteristics play a significant role in determining whether increased connectivity through a transport corridor will spur economic activity around the corridor. Large transport infrastructure investments in countries that have direct access to the sea are more likely to spur economic activity. The size of the country, its terrain, and the level of development appear to have no significant influence.

Some project design characteristics can better stimulate local economic activity. For instance, having a well thought out rationale or theory of change for the project appears to generate significantly more economic activity in the surrounding areas. This is likely because such projects place a larger focus on designing the project in a way that fits the specific needs of its users, which could vary across locals and population groups. The evidence on private sector engagement and involvement suggests that although consulting the private sector on the project design could generate higher WEBs, involving the private sector in the implementation of the project has so far dampened the creation of WEBs. This finding hints at the intricacies that need to be understood by international development organizations and governments for effective engagement of the private sector in corridor projects for greater socioeconomic benefits. On complementary policies and reforms, further research is needed to reach robust conclusions, which would require better proxies than the World Bank DPOs used in the paper.

As the collection and public availability of spatial data on local development outcomes around the world progresses, more studies are needed to shed greater light on how the variation in project design and 18