There are always rumors surrounding gold. One current one has to do with a drop in the number of tons of gold in GLD indicating a "gold bank run" in progress. First chart is price vs tons in GLD over the past year or so, second chart provides more historical perspective.
Next is the number of tons of gold inside the GLD ETF, compared to the tons inside the SLV ETF. The theory is, GLD has been raided for gold in order to repay central bank gold leases. The counter-argument is, people have lost interest in GLD, so the number of tons have decreased on their own. If the counter-argument is true, then SLV and GLD should see relatively similar moves in their inventory tonnages.
A shortage indicator is the current premium or discount over COMEX of gold sold on the Shanghai Gold Exchange.
Another indicator are gold lease rates as well as the gold forward rates.
Next is the famous Commitment of Traders report; these chart shows the net long/short position of the particular group (managed money, producers, swap dealers, other reportables) vs the price of gold. Producers tend to be net short (to hedge production) and managed money tends to be net long.
The gold/silver ratio is one decent indicator of the trend in PM. That's because when PM is climbing, silver is usually doing so faster than gold. Average gold/silver ratio in modern times is about 60; at the 2011 silver peak, it was 30, and at the trough during the 2008 crash, it was 80.
Last is Central Bank buying, mostly Russia and Turkey. This information comes from the IMF, and does not include China. To give you a sense of units and scale, there are: