if you divide paxg by gold (commodity not gld), then you'll notice that there are very tradeable signals. In a perfect world, these would track each other with uncanny precision. That is not the case with this pair. There are times when the relationship is trading in favor of PAXG ie, PAXG is temporarily trading at a premium to the commodity so one could sell PAXG assuming that the price of PAXG will come down to that of GOLD. on the flip side (probably most beneficial) is when the relationship has PAXG trading at a discount to gold. In that case, buying PAXG would give you exposure to the commodity at a discount to par.