On standardization of the Activity Index

Relative Specialization Index (RSI) was introduced as a simple transformation of the Activity Index (AI), the aim of this transformation being standardization of AI, and therefore more straightforward interpretation. RSI is believed to have values between −1 and 1, with −1 meaning no activity of the country (institution) in a certain scientific field, and 1 meaning that the country is only active in the given field. While it is obvious from the definition of RSI that it can never be 1, it is less obvious, and essentially unknown, that its upper limit can be quite far from 1, depending on the scientific field. This is a consequence of the fact that AI has different upper limits for different scientific fields. This means that comparisons of RSIs, or AIs, across fields can be misleading. We therefore believe that RSI should not be used at all. We also show how an appropriate standardization of AI can be achieved.