Methods to account for citation inflation in research evaluation

•The total number of citations is growing annually by 5.6% and thus doubling every 12 years.•Citation inflation is a temporal bias resulting in significant measurement error, which is not addressed by extant normalization methods.•Citation inflation affects longitudinal analysis and comparison of units from different periods.•We outline method to obtain citation deflator index using the Web of Science search portal.•Citation-based research evaluation should be performed using deflated citation values.