  Authorship and citation practices evolve with time and differ by academic
discipline. As such, indicators of research productivity based on citation
records are naturally subject to historical and disciplinary effects. We
observe these effects on a corpus of astronomer career data constructed from a
database of refereed publications. We employ a simple mechanism to measure
research output using author and reference counts available in bibliographic
databases to develop a citation-based indicator of research productivity. The
total research impact (tori) quantifies, for an individual, the total amount of
scholarly work that others have devoted to his/her work, measured in the volume
of research papers. A derived measure, the research impact quotient (riq), is
an age independent measure of an individual's research ability. We demonstrate
that these measures are substantially less vulnerable to temporal debasement
and cross-disciplinary bias than the most popular current measures. The
proposed measures of research impact, tori and riq, have been implemented in
the Smithsonian/NASA Astrophysics Data System.
