Worldwide Usage of the ADS
My paper Use of astronomical literature – A report on usage patterns also discusses the worldwide usage of the SAO/NASA Astrophysics Data System (ADS). The ADS is used by all professional astronomers and astrophysicists in the world, a large and still growing amount of physicists and a huge amount of incidental users, finding their way to the ADS via Google and other general search engines. Usage statistics from our “regular users” (basically people who use the ADS almost daily) allows us to measure the penetration of the ADS in the world and look for trends (if any).
The figure below shows for various countries and regions their usage as fraction of total world usage as a function of GDP per Capita.
Each region has 11 datapoints, corresponding to one year (1997 through 2007). South Africa (ZA) was omitted from the region ”Africa”, because it would completely dominate the analysis for this region (the fraction of world usage for South Africa alone is more than for the rest of Africa).
In the above diagram it is immediately clear that the EU and the USA are different from the other regions. Obviously, for both, the GPC will be higher than the other regions. Since the lion’s share of astronomy research is performed in either the USA or the EU, it is also no surprise that their fraction
of world usage is substantially higher than for the other regions. Significant is
the difference in how the fraction of world usage changes over time. For both the EU and the USA, this fraction gradually decreases over time. The explanation for this is that these two regions represent the bulk of ADS usage (ranging from 84% of world usage in 1997 to 70% in 2007). ADS usage comes from existing Internet users, because in these regions, the number of Internet users is more or less saturated. So, even though there is a steady increase in the number of users in these regions, the fraction decreases because the overall usage increases faster. China displays a similar trend in the recent past, following a period of fast growth (until 2004). The character of the Chinese economy has changed: initially we see growth typical for a low-income region, but probably around 2004, China moved into being a middle-income region. This seems to be the case if we take the number of Internet users as an indicator for economic growth. The number of Internet users in middle- and high-income regions saturates over time (see below). The data points for South America show that there is an increase in ADS usage, even when the economy for that region goes through heavy recession. Around 2002 the fraction settles on a value of about 3%.
Although ADS usage increased in regions like the EU and the USA, the percentage of world usage has decreased for these regions. This is because the growth in World usage is mainly driven by regions with the biggest potential for growth. The density of Internet users reaches a saturation point in middle- and high-income regions at which point ADS usage increases at a slower rate. It is encouraging to see the rapid increase in Internet user density in low-income regions and a similar increase in the number of ADS users in those regions. It indicates that increased access to electronic information is being used and in this sense there is a narrowing of the “Digital Divide” for these regions. Whether this increased access also resulted in an increased scientfic output needs further bibliometric research.