How often should slaves occur?
Just merged the files with my own mod started a game (in which i used the Worldbuilder for quick testing), adopted slavery and defeated about 30 enemies (about 10 barbs, 20 from other civs) - no slaves occured!
\Skodkim
Hmm, odd. Either you were extremely unlucky or the code doesn't work. I'll do some testing. One question though, what units were you killing?