I have a stupid question that is a bit more general than the Saudi case. What's the advantage of selling oil and the using the dollars to buy treasuries or other conservative investment assets? Wouldn't it make much more sense for a country like Saudi Arabia to limit their oil production and finance their deficit of the sales directly instead of using royalties? This assumes that the value of oil will rather rise over time . In addition, for a producer as large as the Saudi's, this strategy should even raise oil prices.