By the admittedly extremely crude measure of the number of bullet points
in the "Notes" section, R7RS-small is about as far from R5RS as R5RS
is from RRRS.  Before RRRS, the language is still recognizable but the
report is not.  I also show the dates of publication.

Since R7RS-small explicitly divides changes into incompatibilities and
extensions, I've tried to do the same for earlier reports, based only
on my own judgements.

RRRS (1985)
    9 incompatibilities + 9 extensions = 18 total changes to
R3RS (1986)
    9 incompatibilities + 11 extensions = 20 total changes to
R4RS (1991)
    2 incompatibilities + 7 extensions = 9 total changes to
R5RS (1998)
    7 incompatibilities + 46 extensions = 53 total changes to
R7RS-small (2013)

R5RS (1998)
    8 incompatibilities + 31 extensions = 39 total changes to
R6RS (2007)

So, as I said, 54 changes in the 12 years from RRRS to R5RS, and almost an equal number
in the 14 years from R5RS to R7RS-small.  But a lot fewer incompatibilities: 20 from
RRRS to R5RS, and only 7 from R5RS to R7RS-small, and 8 to R6RS.

An even more silly question: about how many changes per year?  On the
track leading to R7RS-small, there were 107 changes in 27 years, a mean
of almost 4 changes per year with a standard deviation of 11.6.  On the
track leading to R6RS, there were 93 changes in 21 years, or a mean of
almost 4.5 changes per year with a standard deviation of 10.6.  And now
you can all gang up on me for gross abuse of descriptive statistics.

--
John Cowan    cowan@ccil.org    http://ccil.org/~cowan
If a traveler were informed that such a man [as Lord John Russell] was
leader of the House of Commons, he may well begin to comprehend how the
Egyptians worshiped an insect.  --Benjamin Disraeli

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