Citation measures and impact within astronomy
  By utilising the inbuilt citation counts from NASA's astrophysics data system (ADS) I derive how many citations refereed articles receive as a function of time since publication. After five years, one paper in a hundred has accumulated 91 or more citations, a figure which rises to 145 citations after ten years. By adding up the number of citations active researchers have received over the past five years I have estimated their relative impact upon the field both for raw citations and citations weighted by the number of authors per paper. 
Frazer Pearce