Ngrams: E-portfolios, nursing theory, models of nursing...: Do the lines run true?

For the latest module I'm looking at e-portfolios in nursing education and possibly wider afield. In the FT Weekend Life & Arts there is an extract -

Capitalism’s secret love affair with bureaucracy

- from David Graeber’s book: The Utopia of Rules: On Technology, Stupidity, and the Secret Joys of Bureaucracy published this week on March 12. It includes a graph from Google Books Ngram a word count through time of 'bureaucracy'. I'd read about Ngrams and tried them quite some time ago, but never used them. Now's my chance.

The graph below began with e-portfolio and eportfolio. I tried nursing e-portfolio... but these were not found. With conceptual framework the scale was disrupted. Adding models of nursing and nursing theory provided a frame that also nicely encompasses, at least in this rendering, conceptual space and threshold concepts.

At the risk of asking too much of the graph if not the source, we might be disappointed that models of nursing is not running concurrent with e-portfolio and reassured that nursing theory has waned but is 'still up there'. This is to forget though that the count for e-portfolio here is general not nursing specific.

Ngrams are another tool and a dynamic one no doubt, when the API is utilised, the data downloaded and words are re-examined over time. In answer to the title's question, I do not believe the lines do run true but this is about nursing and e-portfolios.