Frequency of proxy use. Overall, this study has identified 245 ecoinvent v3.8 cut-off datasets (out of 1207 analyzed chemical sector datasets) that use proxy data for heat or electricity. For other purposes, the proxy data is applied even more frequently, but its use is generally very difficult to track due to differences in the documentation and in the implementation of proxies over time. In particular, the datasets from the older ecoinvent versions have seen a variety of individual interpretations of how to implement the proxy data, and these are thus difficult to identify, so the real number of datasets with energy proxy use may be slightly higher. More recently, the energy proxy approach used in the ecoinvent database has also been applied as a core modeling principle in the cm.chemicals database by carbonminds, which is specialized in chemical LCI datasets . Dataset-specific documentation for that database is not available, and customers only receive fully aggregated data; however, the overall documentation suggests that in this database, the datasets of at least 536 out of 1012 chemicals use the energy proxy data from the ecoinvent database (in June 2022) and thus suffer from the same inaccuracy of 20 this approach. GaBi, the third LCI database with a rather broad global chemical dataset coverage, generally does not disclose its input data at that level of detail and therefore may or may not be subject to similar limitations.