  We introduce the first 'living lab' for scholarly recommender systems. This
lab allows recommender-system researchers to conduct online evaluations of
their novel algorithms for scholarly recommendations, i.e., recommendations for
research papers, citations, conferences, research grants, etc. Recommendations
are delivered through the living lab's API to platforms such as reference
management software and digital libraries. The living lab is built on top of
the recommender-system as-a-service Mr. DLib. Current partners are the
reference management software JabRef and the CORE research team. We present the
architecture of Mr. DLib's living lab as well as usage statistics on the first
sixteen months of operating it. During this time, 1,826,643 recommendations
were delivered with an average click-through rate of 0.21%.
