From Hardassetsinvestor.com: At certain times, bullion, represented by the SPDR Gold Shares Trust fares better than miners proxied by the Market Vectors Gold Miners ETF; at other times, the reverse is true. The GLD/GDX ratio reflects the relative strength of gold over mining shares.
There will be times, too, when a broader-based portfolio of commodities will outperform a universe of commodity stocks. I say will because we’re still in the very early stages of tracking an analogue to the GLD/GDX ratio. The Market Vectors RVE Hard Asset Producers ETF , a portfolio of nearly 300 commodity producers or processors, when compared to the GreenHaven Continuous Commodity Index ETF, meters the vigor of hard asset equity investment….. Full Article: Source