How Far is Gas from becoming a Global Commodity?
用小波分析检验天然气市场是否已从区域走向全球，发现欧洲和日本市场虽有一定同步性，但远不及原油市场，且北美市场独立，区域间的同步性主要来自原油价格的传导。
While we can say that there is a global market for crude oil, we cannot say the same for natural gas. There is a strand of literature that argues that, in the last decades, gas markets have become less regional and more global. We use wavelets to test this hypothesis and conclude otherwise: although the European and Japanese gas markets are significantly synchronized, they are much less than the oil markets, which we take as the benchmark. We also show that the North American gas market fluctuations are independent of the other gas markets. Finally, we show that the existing synchronization between gas markets almost vanishes once one filters out the effect of oil price variations, suggesting that it is the global oil market that connects the regional gas markets.