Charting Textbook Costs (Bring in a Mathematician)

An interesting exchange from the CCCOER Community list came from @hofera is request for a simple graphic illustrate the rising cost of textbooks versus consumer price index over time, using as reference:

@waydeo suggested one from Inclusive Access

@phb256 found a simpler one, and even tried to updated it with the data it is based on

And Amy returned to share now what is utterly fascinating when answered by a mathematician, @poritzj in full detail on hys blog post, surfacing that the answer, and maybe the question deserves a different perspective – see Inflation-adjusted Textbook Pain Multiplier for Decision-Makers or [for OER experts] One of the Famous Graphs in the OER World is Backwards

Jonathan makes a case that this well known graph can be misleading, ot not insightful enough “But I actually think this graph is basically backwards [and upside-down, inside-out, and otherwise non-optimal].” – that it is more than the sticker price of textbooks compared to average consumer prices, but that our intuitions need an inflation adjustment, deriving a curve he describes as the “textbook pain multiplier”.

I’ve been re-reading and I keep feeling like I am scraping closer, but not quite getting there. This is a great point to have a conversation here-- is the textbook price versus CPI sufficient?

I even read through Jonathan’s methodological approach (something you rarely see in a news article) that works through the algebra-- I have to respect that and his closing line

[And now you can no longer say that you “never used basic algebra after high school,” since that last bit was solving a simple algebraic equation, as one learns in high school algebra!]"

From just asking for an image you never know what tunnels you will wander down.