Words for God in the Psalms

Going through the psalms at the latter end I've been struck by how regularly Yhwh rather than God (elohim/el) has been used. Here's a quick graph made in Accordance showing Yhwh (yellow) is used more frequently at the beginning and end of the Psalter, while God is used much more in the second fifth of the collection (elohim = dark green; el = blue-green). Just for completion I added in Shaddai and Elyon (in the foreground in red).

It would be interesting to investigate this further, especially as the first book of the psalter is David, but so is the latter part of the second book - perhaps book 1 is David's Yhwh collection and book 2 is David's Elohim collection? It's worth noting the psalms of Korah in book 2 aren't Yhwh psalms, while those in book 3 by Asaph mix it up. And then the exodus collection, the big one (Ps 119), and the psalms of ascent, are all mostly Yhwh psalms.

I know this is all a very broad brush-strokes look, but trying to get the big picture is helpful before zooming in to ask more precise questions.