  National bibliometric performance is commonly measured via relative impact
indicators which appraise absolute national values through a global
environment. Consequenty the resulting impact values mirror changes in the
national performance as well as in its embedding. In order to assess the
importance of the environment in this ratio, we analyse the increase in Chinese
publications as an example for a structural change altering the whole database.
Via a counterfactual comparison we quantify how Chinese publications benefit a
large set of countries on their impact values, identify explanatory factors and
describe the underelying mechanism due to longer reference lists and a
non-uniform citation distribution among recipient countries. We argue that such
structural changes in the environment have to be taken into account for an
unbiased measurement of national bibliometric performance.
