Fascinating analysis, but there are some statistical and methodological flaws in my opinion.
I can buy into the idea of Total Activity being defined by the number of votes, but I find no need to divide it by the number of seats, how would this be relevant to an aggregate metric? Anyway its not a critical flaw if that is a fairly static variable - which it is relatively.
So then we graph out that metric and find it has increased significantly with time - fine. But then we use an increasing metric as the divisor in another calculation to find "Political Activity". Is it thus any wonder we would then find Political Activity is decreasing?
What this proves is that there is a correlation between the number of Senate candidates and the number of Seats, and that both are relatively static.
So, this Analysis does prove something - albeit not exactly what the Author is saying.
What it proves is that in our electoral system we have had a gradually rising total population of Voters over the years, particularly recently, but we haven't increased the number of Senate seats substantially, thus the Candidate number hasn't increased.
And that is a function of a conscious decision to try and keep the Senate as a small body, presumably because of concerns over how a larger Senate would function. And that comes down to the "Size of the Senate" clauses 6-9, in the Election Act 2015, and precursor Acts, the methodology of which encourages a small Senate and effectively limits the size to a maximum of 10.
If we opened the next Senate elections with 11 places, and the next with 15, we would fill them, and more, I suspect, and all these metrics would change consequently.
Thus, in conclusion, the size of the Senate in terms of the number of candidates is intrinsically connected to the number of Seats, in a Supply-Demand type relationship, and the number of seats available is kept artificially low by the System, and hasn't been increased with the growth of the Electorate.
So the "de-politicization" of the Region is thus a conscious decision taken by the legislators who created the Electoral Panel system, and indeed the Panel itself - composed of the Speaker of the Senate, the President of the Republic, and the Office of the Supreme Chancellor. A decision to maintain the "elite" nature of the Senate, to make it more desirable, to increase competition to get into it - rather than to increase participation in it. That, is the root of this trend, not any kind of intrinsic de-politicization of our Culture, imo.