However, the 6-digit HS classification has the advantage that it enables analysis of comparable trade data for almost all countries, and over time.<sup>5</sup> To identify HS 6-digit products associated with the value chains of solar PV, wind turbines and EVs, we followed three steps: First, we undertook a review of the academic and grey literature, finding key papers that have previously identified HS 6-digit products associated with wind turbines, solar PV, and EVs (see Table SI 1 for key sources used). Second, after collating the various HS 6-digit codes for each technology, we drew on further desktop research to classify each product into four value chain segments: raw materials, processed materials, subcomponents, and end products (see Table 5 for a definition of each segment). Third, we validated our product mapping for each green value chain with industry specialists in the supply chains of wind, solar and batteries for EVs. Reviewing the technical specifications of products in these value chains with our product description helped us trim the list of HS 6-digit products for each value chain – and ensured consistency across the three value chains. The final mapping and classification of HS 6-digit codes into value chain segments can be seen in Table 4.

**Table 4: Definitions of value chain segments**

|Value Chain Seg-<br>ment|Definition|
|---|---|
|Raw Materials|Basic materials that are mined, extracted or harvested from the earth. Also referred to as<br>‘unprocessed material’, examples include raw biomass and iron ore. In this link of the sup-<br>ply chain, value added comes from extracting, harvesting, and preparing raw materials for<br>international marketingin substantial volumes.|
|Processed Materi-<br>als|Materials that have been transformed or refined from basic raw materials as an intermedi-<br>ate step in the manufacturing process. Processed materials include steel, glass and cement.<br>In this link of the supply chain, value added comes from processing raw materials into pre-<br>cursors that can be easily transported, stored and used for downstream subcomponent<br>fabrication.|
|Subcomponents|Unique constituent parts or elements that contribute to a finished product. Clean energy<br>technology examples include generation sets for wind turbines and crystalline wafers for<br>crystalline silicon PV modules. Note that what is considered a component by the manufac-<br>turer may be considered the finished product by its supplier. In this link of the supply chain,<br>value added comes from fabricating processed materials into subcomponents that can<br>then be assembled(with other subcomponents)into endproducts|
|End Products|The finished product of the manufacturing process, assembled from subcomponents and<br>readyfor sale to customers as a completed item. Clean energyexamples include|

5 The analysis of value chain relationships, such as determining which input products are used to make other downstream products, generally requires the use of input-output tables or supply chain data. Unfortunately, consistent and comparable input-output or supply chain data is not presently available for products at the 6-digit HS classification. For example, the World Input Output Database (WIOD) currently only covers 43 countries and 56 sectors identified under the International Standard Industrial Classification (ISIC Rev. 4). Only a handful of these countries are developing countries and while a mapping exists from the HS classification to the ISIC classification, too much information is lost when trying to aggregate one classification with around 5,000 products to another with 56 industries. An alternative approach that is sometimes used in the literature is to draw on more detailed input-output data that are only available for certain countries and assume these relationships hold for other countries. For example, a more detailed input-output table (covering 400 industries) is available from the Bureau of Economic Analysis (BEA) for the United States, and this has been mapped to estimate value chain relationships for HS trade data5. However, aggregation issues remain in mapping 400 industries to 5,000 products, and it is questionable whether the input-output relationships of the US are generalizable to other countries.

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