Missing Letters

I have noted recently a couple of articles on letter-counting. Today I decided to count all the letters in the psalter by psalm - just for fun. I threw in Genesis 1 at the bottom of the diagram. My counts are slightly more accurate than reported previously since I am now counting repeated letters in one word, whereas my first cut overlooked these.

What I notice is not worthy of gematria nor of the significance of Ayin so interestingly reported in this article by Ronald Benun. But there is a significant absense of some letters in the Songs of Ascent.

8 psalms are missing the use of gimel
12 are missing zayin
2 missing a het
21 missing a tet (I assume taw is preferred)
16 missing a samek
3 missing a peh
5 missing a sadeh
8 missing a qop
13 missing a sin

The opening of Genesis uses all letters except samek.

The 15 songs of ascent account for 36 of these 88 missing letters or 40%.
That's 144 verses out of 3209 or 4.5%.

I would say there must have been a change in use of the writing system when these psalms were composed or written down. I am sure we could make up some significance to the 88 - after all, it is 1/2 the number of verses in Psalm 119 and 4 times the number of letters in the alefbet. Perfection appended to perfection.