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# Taxonomy  Among the many challenges faced by taxonomy is the difficulty of estimating the size of the task it faces. Estimates of the number of species on Earth are uncertain and inconsistent, and show no signs of converging \cite{Caley_2014}. Some estimates based on models of taxonomic effort suggest that two-thirds of all species have already been described \cite{Costello_2011}. Analyses that use the number of authors per species description as a proxy for effort \cite{Joppa_2011} ignore the global trend for an increasing number of authors per paper \cite{Aboukhalil_2014}, and assume that the effort required per description has remained constant over time. An alternative interpretation is that the quality of taxonomic description is increasing over time \cite{Sangster_2014}, reflecting both increased thoroughness and new technologies \cite{Stoev_2013} \cite{Akkari_2015}.  Rather than try and estimate an unknown (the number of species remaining to be described), we can instead focus on what we know about what we know. In other words, the current state of taxonomic knowledge, which is less than ideal. For example, we currently we lack a comprehensive, global index of species descriptions. For zoology the nearest we have in the Index of Organism Names (ION), which is based on Zoological Record. Fig x shows the numbers of new taxa covered by the ICZN (animals plus some protozoan groups) that have been described each year, based on data from ION. These data show an increase in numbers with dips around the times of the two World Wars, followed by an essentially constant number each year since the mid-twentieth century. The pattern in individual groups may vary considerably. For most of the taxa analysed by \cite{Joppa_2011} the numbers of new species described per year are increasing, but other taxonomic groups are essentially static or in decline.  The rate of progress in biodiversity research is controlled by two factors, the speed with which we can discover and describe biodiversity, and the speed with which we can communicate that information \cite{Pentcheff_2010}. Unlike most biological disciplines, the entire corpus of taxonomic literature since the mid 18th century remains a vital resource for current day research. In this way taxonomy is similar to the digital humanities, where we have not just "big data" but "long data" [978-1594632907]. Not only is this because of the rules of nomenclature that dictate (with some exceptions) that the name to use for a species is the oldest one published, it is also because of the "long tail" effect - for a few species we know a great deal, but for most species the entire sum of our knowledge may reside in the primary taxonomic literature.