Your local averages don't mean much. The actual number of bitcoins an arbitrary fixed configuration will produce will vary anyway with the global level of difficulty set. The more mining that takes place globally the higher the difficulty. The only average is that a new block ( currently 50 BTC, it will be reduced to 25 in the near future ) is mined every 10 minutes or so and this is controlled by the difficulty. So, the more miners, the less of a cut each miner gets, the total output of all miners is the same. Maybe no one should mine, then the difficulty would be quite low