  Park et al. [1] reported a decline in the disruptiveness of scientific and
technological knowledge over time. Their main finding is based on the
computation of CD indices, a measure of disruption in citation networks [2],
across almost 45 million papers and 3.9 million patents. Due to a factual
plotting mistake, database entries with zero references were omitted in the CD
index distributions, hiding a large number of outliers with a maximum CD index
of one, while keeping them in the analysis [1]. Our reanalysis shows that the
reported decline in disruptiveness can be attributed to a relative decline of
these database entries with zero references. Notably, this was not caught by
the robustness checks included in the manuscript. The regression adjustment
fails to control for the hidden outliers as they correspond to a discontinuity
in the CD index. Proper evaluation of the Monte-Carlo simulations reveals that,
because of the preservation of the hidden outliers, even random citation
behaviour replicates the observed decline in disruptiveness. Finally, while
these papers and patents with supposedly zero references are the hidden drivers
of the reported decline, their source documents predominantly do make
references, exposing them as pure dataset artefacts.
