Evaluation of researchers is a big issue in institutional research. We propose a method for quantitatively evaluating the stage of young, middle and senior researchers focusing on the role of the last author in co-authored papers. We trace the two time series of the number of published papers and the ratio of the last authored papers among them of each researcher. We conducted experiments on 84 researchers of ICT related graduate school of a university in Japan, and on 50 researchers who published papers in 15 highly evaluated international conferences and 5 international journals. We analyzed 3360 articles in the first case and 13138 articles in the second case. We test three different approaches: cross tables, portfolios and bar graphs.
