The trading of carbon dioxide emissions can cut costs for countries meeting Kyoto Protocol targets. A study looked at how this trading affects both industrial and developing nations. When countries trade, costs to meet targets drop by around 50%. Even though developing countries don't trade, they feel the impact. Oil prices and demand for their exports go up with trading. If developing nations set caps and trade with industrial countries, the benefits could be huge. A global emissions trading market might cut costs by almost 90%, if it works fairly. But in real markets, buyers tend to get more benefits than sellers. Even with limited permits, trading can still help industrial countries meet targets at lower costs, while also giving profits to developing nations selling permits.