After careful forensic analysis, I have concluded the entire thing was created by a single person. I call this the One Author Theory (OAT). Let me present to you OAT's evidence.
First, notice almost every tally is similar to its immediate neighbors. They have the same color and the same thickness. This suggests the tallies were all made with the same marker and with similar techniques.
We can see similar techniques elsewhere. First, notice that each category has tallies. Then, within each category (for example shit), focus on the rightmost tallies. Notice that the tallies tend to curve in a similar way. This suggests those tallies were created under similar conditions, with a similar technique.
You may have noticed that the piss tallies are thicker and straighter than the jerk it tallies. This may suggest my One Author theory is wrong, but my theory does incorporate this fact. The fact is explained by a change in technique. Therefore, the OAT cannot stand on its own. It requires another theory to grab onto. This other theory is the Progressive Degradation of Commitment (PDC) Theory.
I will now give evidence for the PDC Theory. Notice the shit category. Its topmost row has a consistent left-to-right pattern. The tallies become smaller and smaller. They also become curved at the end. This suggests a consistent loss of commitment.
The PDC Theory appears to struggle with the jerk it category. After all, the bottom row starts with small tallies and progressively has its tallies grow tall and straight. This we shall call the Jerk It Anomaly (JIA). However, concluding that the JIA proves that the PDC Theory fails is incorrect. If one uses the PDC Theory correctly, it can actually explain the JIA.
How? First, we need to remember that the PDC Theory shouldn't be limited to rows. We saw an example of this when PDC Theory explained piss' thickness in relation to jerk it's thickness. In other words, PDC Theory can scale. It can explain rows of tallies but it can also explain columns of categories. So, if we apply PDC Theory to the entire work, we can assume that the entirety of the last column (jerk it) was built with little commitment. The author could've been pressured for time. It is reasonable to speculate that the author felt a sudden urge to attend to his unfinished business, be it pissing, vaping, shitting, or jerking it. In either case, the PDC Theory comes out intact.
Ultimately, the OAT uses the PDC Theory to address validity threats like the JIA. The author may have attempted to dupe us into thinking the census was representative of a population. However, the One Author Theory lets us see that the author's work is more representative of their purposes, capabilities, and proclivities.
It's important to note that this does not necessarily reduce the author's merit and the piece's impact. Future studies could evaluate to what extent this apparent census creates a sense of community and connection in the bathroom-stall goers. I, for one, would appreciate going to the bathroom and finding this piece. I wouldn’t necessarily appreciate vaping or jerking it, but I would appreciate shitting or pissing next to it.