# **1. Introduction**

In recent years, containerized trade, the backbone of global value chains, has experienced unprecedented disruptions. For instance, the COVID-19 pandemic created unforeseen consequences in a far-ranging array of sectors on a global scale, triggering an unprecedented supply chain crisis from late 2020 to mid-2022. Surging trade demand surpassed shipping capacity, itself affected by massive operational disruptions in key ports. In 2023, there were two events of global relevance. First, a severe drought affected the operation of the locks in the Panama Canal, resulting in a reduction in throughput and restricting the size of vessels able to transit the canal. Later in the year, militant groups carried out attacks in the Red Sea, forcing shipping lines to reroute ships servicing the Asia-Europe and Asia-US East Coast trade routes through the Cape of Good Hope.

In contrast to typical localized events impacting supply and logistics chains, the recent disruptions have been geographically extensive, long-lasting in duration, and multi-faceted – impacting demand patterns, manufacturing, maritime logistics, port operations, and freight distribution in complex ways. For decades, the container shipping network has operated loop services according to a regular schedule, like passenger rail or air services. Schedule predictability helps deal with trade imbalances, where surpluses in some regions offset deficits in others. This container supply/demand mismatch means that about 20 percent of total container movements are empty repositioning voyages. When disruptions hit, delays in repositioning containers may amplify the effect of ship delays (section 4).

A key challenge lies in quantifying the stress levels global container ports are facing through a unified metric that can be precisely measured and utilized as a meaningful indicator. To fill this gap, the Global Supply Chain Stress Index (GSCSI) is proposed as a measure capturing the delayed container shipping capacity across global maritime ports. This stress metric, which has been published in the World Bank’s Trade Watch since late 2021, is inherently port-centric and derived from analyzing container shipping traffic flows. The index is computed monthly and can be aggregated from port-level data into regional or global indices. It focuses specifically on container vessels of the Panamax class and larger operating on intercontinental liner services. Feeder loops exhibit, by nature, higher volatility and have not been included in the initial scope. Therefore, the index does not yet fully capture port stress across the entire shipping network as ports being solely called by ships of lower capacity than Panamax are not included.

Measuring and understanding the impacts and propagation of supply chain disruptions has gained significant attention, especially since the 2021-2022 supply chain crisis. Most efforts in this domain have originated from private sector initiatives and publications (e.g., shipping lines and operators, as well as maritime research consultancies), with only a few predating the crisis. The increasing availability of vessel tracking data and schedule information has facilitated these endeavors since this type of information recently became available. However, in contrast, economic literature tackling these topics or providing an empirically testable theoretical framework remains limited, with few exceptions (e.g. Bai, et al. 2024). Notably, a fundamental question as central as the evident connection between freight rates and supply chain disruptions has not been comprehensively covered in prior literature (Notteboom et al., 2021; Rodrigue, 2022).

Indicators quantifying supply chain disruptions generally fall into three broad categories (Table 1): (1) surveys of supply chain professionals, (2) indicators derived from tracking or schedule data, and (3) metaindicators aggregating existing data series, based on expert knowledge. Other noteworthy tools are those visualizing vessel movements, including the IMF Port Watch and similar tools by maritime consultancies.

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