One example of USU effects, formulated by considering measurements of neutron-induced fission cross-section ratios of 238 U/ 235 U, highlighted the point that different USU estimation approaches result in slightly different but yet consistent evaluated mean values and uncertainties. Under/overestimation of reported uncertainties have been found. This example illustrated the subjective nature of estimating the effect of USU. However, this subjectivity does not apply only to estimating USU effects but also holds true for evaluating mean values and covariances in general. After all, these derived values depend on the evaluation techniques utilized, input **data** selected and subjective choices made on the parameters of models, corrections of experimental **data** and on methods for estimating covariances of both, model and experiment. Hence, our evaluated results are always subjective-with and without consideration of USU. However, if one neglects adding obviously necessary contributions from USU to uncertainties of input data, the evaluated mean values might be more biased and the evaluated uncertainties will be underestimated, in turn, adversely impacting application calculations.