Based on bibliographic information, the annual contribution of each country to the expansion of CS was calculated by considering the share of the number of substances reported by each country in the respective year. For example, if a paper authored by three scientists reports one new substance and two of the authors have affiliation to a Chinese institution and the third one to an American institution, we assign 2/3 of substances to China and 1/3 substances to the US. Thus, if for a given year , there are new reported chemicals, country contribution to the CS of year is given by , where represents the number of authors of country that published substance for the first time in year and accounts for the number of authors participating in the publication of substance on year . The complete list of values is shown in file data/raw/Country_weighted_allSubs.tsv (SI).