The above chart was recently published on Reddit. ( Source: r/dataisbeautiful )
The author of the reddit thread cites the following data sources:
I'm interested in verification if the overall picture is accurate, hugely exaggerated, or even underestimating the real trend.
I'm not doubtful of the correctness of the data, as the data source could be considered a generally trustworthy one.
However, what I don't know is how well this data reflects the reality of students today. How "complete" is this set of data, and are the books making up the majority of that data really the same ones used as textbooks in universities and schools? In short: Are these really representative values? I also could not find the information which books exactly make up the index.
In short, my skepticisms is aimed at the interpretation of the data more than the actual values used to produce it. In particular so, as the apparent 'take-home' message of the chart is very, very strong.