> Interesting. I went back and checked the text files that I used and
> they were all 8-bit ANSI. I started with 5.9MB which compressed to 0.3MB
> - vastly different than your experience, 5.8MB to 2+MB. In fact, I can't
> remember getting such low compression as you did.
>
> I am running 7z v9.22 beta with default level. You?
>
I did my tests with 7z v9.20 but just reran them with 7z 9.38 beta with almost identical results. However I also tried making solid archives. With the 325 text files that produced a noticeable improvement (1.35MB rather than 1.98MB). With the nandroid backup it also produced a small improvement: 446MB instead of 461MB. I expect that is because these backups consist of two very large files and 6 small ones, so the overhead of making files individually replaceable is small.
I have never achieved the compression rates you have, and I notice that 7-Zip's author only claims 30%-70% improvement over ZIP.