Number of unique words in four novels by Toni Morrison

[Some preliminary notes on a project that my brother Kenton and I are working on. Thanks to poet/professor Opal Moore for the nudge.] 

Have you ever thought about Toni Morrison's word usage, and specifically the number of unique words she uses in multiple novels? I was curious, and decided to do a few measurements.

For the purposes of comparison, I needed a baseline, so I took a look at the first 5,000 words in two of Morrison's novels: The Bluest Eye (1970) and Beloved (1987). Off the top, before any calculations, I assumed that Beloved would have the most extensive vocabulary, mainly because it's one of the most critically-acclaimed American and African American novels. 

My assumption was wrong.  

Take a look. 

At about 1,515 unique words, The Bluest Eye has more diverse word usage or a more vaired vocabulary than Beloved at 1,336. It's possible that the different approaches to the storytelling explain the difference. Still, for some reason I expected an author's later novel, Beloved, to have more diverse word usage than the writer's debut. 

I later added Sula (1973) to the mix. It contains 1,563 unique words, topping both The Bluest Eye and Beloved. And later still, I added Paradise (1997), which contains 1,788 unique words among the first 5,000 words of the novel. 

The number and variety of word usage give us ways of thinking about elements of novels beyond our conventional approaches to literary analysis.  These numbers don't tell us whether one novel is better than another one, but they do give us some indications concerning how writers use words. Gaining more information on black word usage can of course be useful.