That China, one of the lowest income 
countries in the world at the turn of the 21st century, became a 
super-power in scientific knowledge in less than two decades is a 
remarkable development in the history of science. The way China deploys 
its newly developed scientific resources will drive the direction of 
science and technology into the foreseeable future and the direction of 
our increasingly knowledge-based economy. 
From
 2000 to 2016, China jumped from bit player to star performer in 
physical science and engineering (S&E) research. As Xie, Zhang and 
Lai (2014) document, China invested heavily in S&E in the 2000s, 
becoming a world leader in bachelor’s and master’s degrees and a huge 
producer of S&E PhDs and became the biggest source of international 
students, who earn S&E PhDs in the US and other advanced countries. 
It also increased its R&D and number of researchers hugely. The 
country’s R&D spending exceeded EU spending and should surpass US 
spending by 2020 at the latest.
The
 investment in scientific resources paid off in a huge rise in China’s 
share of scientific papers and citations in the Scopus database that 
indexes global scientific publications. In 2000, Chinese addresses 
accounted for 4% of papers and less than 2% of citations. China topped 
the US in number of papers published in 2016, generating headlines 
(Tolleson, 2018). Impressive as these statistics are, our research (Xie 
and Freeman, 2018) shows that they massively understate China’s 
contribution to global science in two ways. 
 
First,
 measures of scientific contribution by the address of researchers gives
 China no credit for papers written by Chinese researchers with 
non-Chinese addresses.  It counts a paper with, say, five Chinese named 
authors working in the US as a US paper just as it would a paper with 
five authors having American names. The missing contribution is large, 
as China’s diaspora research community is such that in 2016 17% of 
non-China addressed articles had at least one Chinese named author.
 
To
 take account of Chinese researchers working outside China, we modify 
the standard address-based measure of contribution with an 
address-and-names metric that gives ½ credit for China’s share of 
addresses and ½ credit for Chinese share of names on a paper. We 
distinguish persons from China by first names as well as surnames, 
counting Xu Wang as from China but not David Wang.  Since nearly all 
names on China addressed papers are Chinese, while many non-Chinese 
addresses have a Chinese named author, the adjustment increases China’s 
share of papers.  It raises China’s share in 2016 by nearly one third, 
from 18.0% of papers in the weighted address measure to 23.3% of papers 
in the address-and-names measure.
 
Second,
 while Scopus includes some Chinese journals in its bibliometry, over 
80% of its journals are in English, and it covers only 8% of the 4,216 
science, engineering, and math journals that the China National 
Knowledge Infrastructure (CNKI) reports as published in China. Scopus 
presumably chose outstanding Chinese journals for inclusion, but the 
journals excluded from its database almost certainly contain some useful
 and interesting science. In any case, the magnitude of the missing 
scientific papers is huge. As Figure 1 shows, CNKI journals published approximately the same number of 
articles (1.6 million) in 2016 as Scopus – the results of a huge 
increase in CNKI publications beginning in the 1980s.
	Figure 1:  Numbers of S&E Journal Articles in Scopus and in CNKI, 1980-2016.
If
 the scientific content/impact of Chinese language papers was on a par 
with that of English or other language papers in Scopus, the roughly 
equal number of CNKI and Scopus articles would imply that China was 
responsible for about 2/3rd’s of scientific work in 2016:  ½ from CNKI 
journals and ~ 1/3 of the ½ from Scopus. 
 
But
 CNKI articles do not have the same quality/impact as international 
journal articles. Fewer scientists read Chinese than English. CNKI 
papers are shorter and have fewer references than Scopus papers. China’s
 requirement that PhD’s and master’s candidates publish thesis papers 
for a degree leads to many publications with a narrow scope that would 
elsewhere place them in university libraries. Indicative of the quality 
difference, 44.6% of CNKI papers published in 2013 received no citations
 in the succeeding three years compared to 29.0% of Scopus papers 
published in 2013.  Recognizing the higher impact/quality of English 
language publications, Chinese universities offer sizable incentives for
 publishing in English language journals, which induces researchers to 
send their best work overseas.
 
To
 take account of the missing Chinese scientific literature and obtain a 
valid estimate of China’s contribution to science worldwide, we need an 
“exchange rate” measure of comparability between publications in the two
 databases. How valuable is a CNKI article relative to a Scopus article 
in contributing to science?
 
We
 use citations to answer this question. While imperfect, citations are 
the most widely used and objective indicator of the quality/impact of an
 article. We focus on papers published in 2013, which allows at least 
three-year forward citations in our data. Both Scopus and the CNKI count
 citations within their own database. A 2013 Scopus journal article 
averaged 9.2 forward citations from other Scopus articles while a 2013 
CNKI journal article averaged 2.3 forward citations from other CNKI 
articles. This suggests a citation-based exchange rate of about 0.25 (= 
2.3/9.2) for CNKI articles compared to Scopus articles. 
 
But
 this excludes citations across the databases, which neither database 
counts.  To estimate cross-database citations, we drew random samples of
 2000 non-Chinese language Scopus papers and of 500 Chinese language 
papers in CNKI from 2013 to 2017 and counted their references to 2013 
publications. References are, by definition, backward citations from 
later papers to earlier papers, and thus the forward citations of 
earlier papers.  CNKI papers are far more likely to cite Scopus articles
 than the reverse. About half of journal references in CNKI articles to 
2013 publications were to Scopus articles, while just 0.29% of journal 
references in Scopus articles to 2013 publications were to CNKI Chinese 
language papers. Extrapolating, we estimate that 2013 Scopus articles 
received 3,276,350 citations from CNKI articles through 2017 whereas 
2013 CNKI articles received l32,196 citations from non-Chinese language 
Scopus articles. Adding these citations to the number of citations in 
Scopus and CNKI reduces the exchange rate of a CNKI journal article from
 0.25 to 0.20 of a Scopus paper. Valuing a CNKI publication at 1/5th of a
 Scopus publication we estimated the total number of Scopus equivalent 
papers in the two data sets and found that China contributed 36% of 
these articles.
Rising quality of Chinese scientific research
 
We
 explored further the quality of Chinese scientific articles in the 
Scopus database by analyzing the citations those papers received from 
other Scopus papers.  In 2000, papers with all-Chinese addresses 
received just 29% of the world average of citations while international 
collaborations and papers with Chinese names working at non-Chinese 
addresses received more citations than the world average. The best 
research by Chinese scientists was being conducted outside of China. By 
2013, citations to papers with all-China addresses increased to 70% of 
the global average while collaborative work and work done outside China 
converged toward the average. China’s share of global citations rose 
from 7.4% in 2000 to 19.5% in 2013, due primarily to the increased share
 of citations to all-China addressed papers. 
 
As
 a final look at the quality of China’s contribution to science, we 
examined the percentage of Chinese names and Chinese addresses in papers
 published in Nature and Science.  In 2016, about 20% of names on papers
 in these journals were Chinese while 8% to 9% of addresses were Chinese
 – far above 7-8% of names and 0.5% of addresses in 2000. 
 
In
 total, we estimate that China obtained 37% of Scopus equivalent 
citations. With 18% of the world’s population and world GDP, China’s 36%
 of 2016 papers and 37% of 2013 citations show that it is essentially 
contributing twice its weight to the advance of science. While our 
calculations ignore scientific articles outside Scopus in languages 
other than Chinese, we estimate that taking account of these would lower
 our estimated China contribution by less than 3 to 4 percentage 
points. 
Conclusion
 
That
 China, one of the lowest income countries in the world at the turn of 
the 21st century, became a super-power in scientific knowledge in less 
than two decades is a remarkable development in the history of science. 
The way China deploys its newly developed scientific resources will 
drive the direction of science and technology into the foreseeable 
future and the direction of our increasingly knowledge-based economy. In
 the 19th century, Horace Greeley famously advised Americans to “Go 
West, young man, and grow up with the country.” In the 21st century, 
science is going East and will grow up with China.
(Qingnan
 Xie, Nanjing University of Science &Technology & Labor and 
Worklife Program, Harvard Law School; Richard B. Freeman, Harvard & 
the NBER.)
	
	
References
Tollefson, Jeff (2018). “China Declared World’s Largest Producer of Scientific Articles,” Nature, News, 553 (25 January): 390. doi.org/10.1038/d41586-018-00927-4
Xie,
 Qingnan, and Richard B. Freeman (2018). “Bigger than You Thought: 
China’s Contribution to Scientific Publications,” NBER Working Paper 
24829 (July).
	Xie, Yu, Chunni Zhang, and Qing Lai (2014). “China’s Rise as a Major Contributor to Science and Technology,” PNAS 111(26) (July): 9437-9442. doi.org/10.1073/pnas.1407709111.