  Bibliometrics is successful in measuring impact, because the target is
clearly defined: the publishing scientist who is still active and working.
Thus, citations are a target-oriented metric which measures impact on science.
In contrast, societal impact measurements based on altmetrics are as a rule
intended to measure impact in a broad sense on all areas of society (e.g.
science, culture, politics, and economics). This tendency is especially
reflected in the efforts to design composite indicators (e.g. the Altmetric
attention score). We deem appropriate that not only the impact measurement
using citations is target-oriented (citations measure the impact of papers on
scientists), but also the measurement of impact using altmetrics. Impact
measurements only make sense, if the target group - the recipient of academic
papers - is clearly defined. Thus, we extend in this study the field-normalized
reader impact indicator proposed by us in an earlier study, which is based on
Mendeley data (the mean normalized reader score, MNRS), to a target-oriented
field-normalized impact indicator (e.g., MNRS_ED measures reader impact on the
sector of educational donation, i.e., teaching). This indicator can show - as
demonstrated in empirical examples - the ability of journals, countries, and
academic institutions to publish papers which are below or above the average
impact of papers on a specific sector in society (e.g., the educational or
teaching sector). For example, the method allows to measure the impact of
scientific papers on students - controlling for the field in which the papers
have been published and their publication year.
