The takeaway from US Global Investors' just-updated Periodic Table Of Commodities Returns is that there is no single best commodity to invest in. Indeed, annual returns can be extremely volatile. Take coal:  In 2007, it had returns of +97 percent.  The next two years saw pretty bearish results, while the two years after that proved bullish. And last year? Coal was the worst-performing commodity of all the ones the firm tracks, at -16 percent. From US Funds' Frank Holmes. This table shows the ebb and flow of commodity prices over the past decade and illustrates the principle of mean ... Read More