We investigated the extent to which observers rate clearly visible postures on video differently from postures that are only partly visible, and whether this would have an effect on full-shift posture summaries. Trunk and upper arm postures were observed from 10,413 video frames representing 80 shifts of baggage handling; observers reported whether postures were fully or only partly visible.  Postures were summarized for each shift into several standard metrics using all available data, only fully visible frames, or only partly visible frames. 78% of trunk and 71% of upper arm postural observations were inferred.  When based on all data, mean and 90^th percentile trunk postures were 1.3° and 5.4° lower, respectively, than when based only on fully visible situations.  For the arm; differences in mean and 90^thpercentile were 2.5° and 8.1°.  Daily posture summaries can, thus, be significantly influenced by whether partly visible postures are included or not