I wonder if we could create a currency that tracks the number of people in the world. The historic problem with gold was that the real, physical economy could grow faster than the supply of gold that represented it. The problem/feature of bitcoin is that the economy accessible through bitcoin is growing much faster than the currency is produced, hence the ridiculous rise in the exchange rate of a single bitcoin. The ultimate upper bound on the value of a bitcoin is the world GDP divided by 21 million
