obstacles (e.g. rough terrain) or other barriers (e.g. border delays), and relative performance measures (e.g. processing time at ports or when crossing a border).

As with any modeling exercise, it should be noted that our network is a simplified version of reality and results are affected by the quality of inputs. For example, we do not include some elements that could affect routing, such as rail gauge, freight or passenger lines, service frequency, etc. An additional limitation that needs to be acknowledged comes from the fact that the Belt and Road Initiative includes some efforts that are not easily introduced to the network: improving efficiency of customs, special economic zones, reducing border delays or an improved management of economic corridors. As an extension of our main database, in Section 5 we present two scenarios where those elements are explicitly taken into account. Finally, our results are driven by a number of assumptions regarding the speed along different path as well as the choice of transportation mode, the processing time when reaching a port and the time it takes to cross a border. We describe those assumptions in detail below.

# **b. Transport network and BRI‐related transport infrastructure projects**

We start with an initial network of links connecting all cities considered in our analysis, and we then add additional links and improved speed corresponding to transport infrastructure projects that are linked to the Belt and Road Initiative. Our initial network comes from Delorme Atlas of the Earth (DAE), 2015 release. For our analysis, maritime features were generated separately for the Pacific, Atlantic and Indian Oceans, and for the Caribbean Basin and Seas of Indonesia. To simulate plausible trans‐oceanic shipping routes, great‐circle arcs<sup>7</sup> were generated from port locations along the boundary of Exclusive Economic Zones. Within the Caribbean Basin, around Indonesia, and near land, connectivity to major ports was manually digitized using a map of Global Shipping Routes (ESRI, CIA, 2012).

When building our estimates of shipping time reductions that can be associated with the BRI, we need to enrich the current transportation network with planned projects. Compiling a list of transport infrastructure projects associated with the BRI is a delicate task since there is no one criterion that could be used to define what is or is not part of the initiative. In particular, there might be projects financed by loans from China that might not necessarily fall under the BRI, and there might be projects with non‐ Chinese funding that are still considered in some sources as being part of the BRI.

We start from the list of infrastructure projects developed by Reed and Trubetskoy (2018) and which considers projects respecting all three following criteria:

1. The project is explicitly mentioned in one of the following sources as being part of BRI: either document issued by a government (including government press agencies), or article in a major academic journal or global news source or a quote by a government official in a reputable news source.

2. The project is at least in the planning phase.

3. The project impacts travel between two cities of at least 300,000 inhabitants.

These criteria present the advantage of restricting our list to projects that have been indeed related to the BRI and to exclude some projects for which feasibility might be in question. For example, condition 2

> 7 Shortest distance between two points on the surface of a sphere, measured along the surface of the sphere.

6