Although the relational approach to the study of GVCs is concerned with the same phenomena as the more traditional approach discussed earlier in this paper, these literatures have largely evolved in isolation. These separate paths are partly explained by the significantly different sources of data used in these different literatures, as discussed next.

# 4.1 Measurement

Measuring participation of firms in relational GVCs is notoriously diffi cult. First of all, because relational GVCs activity entails firm-to-firm links, it presents the same diffi culties outlined in section 3 regarding measuring participation at the firm level. But more importantly, the distinctive characteristics of relational GVCs call for a narrower empirical definition of this type of GVCs, one that excludes firm-level GVC participation associated with the exchange of fairly homogeneous goods in spot transaction.

Given these diffi culties, it is no surprise that progress on this area has been rather scant. The most influential work on the relational nature of GVCs tends to focus on particular case studies of specific sectors and countries, which allow the researcher to paint a more colorful and realistic picture of the web of relationship sustaining global production in that sector. The extensive and influential of Gary Gereffi provides a good example of this (see for instance, Gereffi , 1994, on the apparel industry, Sturgeon et al., 2008, on the automobile industry or Bamber and Gereffi , 2013, on the medical device industry in Costa Rica). More recently, Rocco Macchiavello and Ameet Morjaria have studied in detail the relational nature of contracting in various agricultural markets in less developed economies, such as their work on the flower industry in Kenya (see Macchiavello and Morjaria, 2013) or their work on the coffee value chain in Rwanda (Machiavello and Morjaria, 2019).

One of the initial goals of the 2020 World Development Report was to attempt to provide a bridge between this case-study-based literature and the broader empirical literature on GVC participation. The idea was to develop firm-level and product-level measures of the extent to which the GVC participation of firms is relational in nature, and the extent to which international transactions associated with a given product tend to be relational in nature. More specifically, the aim was to exploit the panel nature of some of the datasets available from the World Bank’s Exporter Dynamics Database (EDD) to construct measures of the observed persistence of firmto-firm transactions, perhaps partialling out various natural determinants of persistence (such as exchange rate volatility). This is very much in line with the measure of “relationship stickiness” proposed by Martin et al. (2018), which they compute using detailed firm-to-firm export data from France. The hope was to “scale up”this approach and apply it to various countries, with the initial goal of verifying whether there was a significant positive rank-correlation in product-level stickiness across countries. Such a finding would indicate that there is a significant product-level dimension to stickiness that is likely to render GVC participation in certain goods particularly prone to be relational in nature. With such finding at hand, one could use standard industry concordances to construct a global Input-Output table that separates trade flows associated with traditional 21