Using time dependent citation rates (sales curves) for comparing   scientific impacts
  As a simple means for comparing and - if possible - predicting scientific impacts of different researchers working in the same field, we suggest comparing their "sales curves". A sales curve is the number of citations of the researcher's papers per year, the citation rate, considered as a function of time. As examples, we present the citation histories of 10 older well-cited scientists working in the same field. The sales curve is found to be highly individual, that is, there is a large variation between different scientists' sales curves. For each well-cited scientist, however, the sales curve is steadily increasing as long as he is young and active, and its slope, the citation acceleration, contains the essential information about his impact. The slope averaged over the time of activity of the scientist is roughly independent of time and is a fairly age-independent measure of his scientific impact. In physics and chemistry, well-cited active scientists have time-averaged citation accelerations at the order of 10 citations per year^2 or more. The normal citation acceleration is an order of magnitude smaller. We also show the sales curves for three large research institutes whose sizes have been fairly constant over the last 35 years. These sales curves are quite linear and have slopes at the order of 1 citation per scientist per year^2. 
Werner Marx, Hermann Schier, Ole Krogh Andersen