Gold vs Silver

I like to study the relationship between the price of gold and silver.  I review the charts for two popular exchange traded funds to do this - IShares Silver Trust ETF (SLV) and SPDR Gold ETF (GLD).  In the past, I recommended the purchase of silver, especially when silver's rate of appreciation was trailing gold by a significant margin - approximately six months ago.  As you can see in the chart, not only has silver closed the gap, it's level of appreciation has greatly exceeded gold.  That would indicate that either silver is now overpriced or gold is underpriced and needs to catch up.  I wouldn't recommend adding to silver investments at this time.