  Using the ESO Telescope Bibliography database telbib, we have investigated
the percentage of ESO data papers that were submitted to the arXiv/astro-ph
e-print server and that are therefore free to read. Our study revealed an
availability of up to 96% of telbib papers on arXiv over the years 2010 to
2017. We also compared the citation counts of arXiv vs. non-arXiv papers and
found that on average, papers submitted to arXiv are cited 2.8 times more often
than those not on arXiv. While simulations suggest that these findings are
statistically significant, we cannot yet draw firm conclusions as to the main
cause of these differences.
