Total number of possible gismu forms: 96,475
Total number of possible forms excluding the last vowel: 19,295
Total number of official gismu: 1,342
Total number of gismu forms that clash with official gismu: 11,874
(according to the definition of which gismu clash with each other in the book, including the forms of the official gismu themselves)
Percentage of forms actually taken: 12.31 (about 1 in 8)
(whether by clashes or by the actual gismu themselves)
Percentage of forms actually taken (ignoring clashes other than the last vowel): 6.96
(about 1 in 15)
I get a different analysis, as follows:
If this is correct, then we can't have a distinct gismu for every culture, because the number of languages spoken around the world is 6000-7000, depending on how you count.
b blocks p, v
c blocks j, s
d blocks t
f blocks v, p
g blocks k, x
j blocks c, z
k blocks g, x
l blocks r
m blocks n
n blocks m
p blocks b, f
r blocks l
s blocks z, c
t blocks d
v blocks b, f
x blocks g, k
z blocks j, s
Enough speculation! I have written a program that by brute force actually counts the number of free gismu. I started by generating a list of all 96475 possible gismu forms. We can call 'em "candidate gismu" or "proto-gismu". I then went through the list of 1342 official gismu, one at a time. For each one, I deleted it from the list of proto-gismu. Then I deleted all the proto-gismu that differed only by the final vowel (except for the "brodV" series (are there any other exceptions like this?)). Then I deleted all the proto-gismu that were blocked based on consonant similarity as in the table given just above. When I had done that for all the official gismu I counted the remaining proto-gismu. (On my Pentium III 450 running Windoze 98 all this takes less than a minute.)
The answer was rather surprising. I find that there are still 85,536 available gismu forms. Now, I'm sure you'll say, "That's simply not possible!" But think about it. A lot of the forms that would be blocked by the consonant similarity rules aren't even valid proto-gismu. (Don't forget, to be a valid proto-gismu a form still has to conform to certain rules.) So fewer forms are blocked than you might think. Additionally, a number of forms (no, I haven't counted them; maybe later) are blocked multiple ways. For instance, *bajru is blocked by both bacru and bajra. Because of this overlap fewer forms are blocked than you might think.
I'm pretty confident that my program is correct, but it would be a Good Thing if someone were to attempt to verify my results. --mi'e skat