  We investigate the problem of choice overload - the difficulty of making a
decision when faced with many options - when displaying related-article
recommendations in digital libraries. So far, research regarding to how many
items should be displayed has mostly been done in the fields of media
recommendations and search engines. We analyze the number of recommendations in
current digital libraries. When browsing fullscreen with a laptop or desktop
PC, all display a fixed number of recommendations. 72% display three, four, or
five recommendations, none display more than ten. We provide results from an
empirical evaluation conducted with GESIS' digital library Sowiport, with
recommendations delivered by recommendations-as-a-service provider Mr. DLib. We
use click-through rate as a measure of recommendation effectiveness based on
3.4 million delivered recommendations. Our results show lower click-through
rates for higher numbers of recommendations and twice as many clicked
recommendations when displaying ten instead of one related-articles. Our
results indicate that users might quickly feel overloaded by choice.
