Class population

Has anyone managed to effectively raise or lower a certain class population? I notice in my game that I have so far that perhaps it flucuates up and down every now and then, but the poor stay usually around 25-30, the middle around 40-45, the wealthy 25-30. Has anyone managed to effectively make one class population larger/smaller permanently?

I managed to get religious down to zero in my last game. Took a long time to do though. I also got motorist down from about 80% to 20%. Ethnic minorities also went from about 25% to near 100% without me trying to do anything specifically to encourage them, once GDP got high enough immigration just took off.