User blog comment:Mohrpheus/Spiritual Imbalance in Bleach - The End of the World?!/@comment-1932702-20100901104153/@comment-1268838-20100901113319

I suppose that new souls can be produced, because there's a flaw with the reincarnation system. For it to work, each and every birth in the Human world has to correlate with the death of a soul in the Soul Society - the chances of that being possible are slim to none. Furthermore, souls are capable of producing children - where would that soul come from? Considering this, the only conclusion would be that, as you said, new souls are created for some births, whereas others are a stage of reincarnation. And so, even if Hollows eat souls by the millions over a span of centuries, the souls can be replenished. In that way, balance can be maintained. Of course, this is all speculation, but it's interesting to think about.