Hi THUCYDIDES79, welcome to the Panda Forum. I think the chart you are referring to is this one, yes? Source: http://www.pandacollector.com/pricepedia-index.html If so, I might hazard a few answers. Hopefully PandaCollector will give his official response: Q> Reasons that the PPI (Panda Price Index) is used as a selling/marketing point on ALL coins? A few things that should be understood prior to answering the question: 1. The PPI isn't meant to directly infer performance on all coins. Just like the DOW Jones Index and S&P 500 doesn't cover ALL the stocks performance. The PPI is only an index of 20 Pandas with mintages less than 2000. 2. What the PPI does provide indirectly, is a snapshot of the demand for the Panda market. If these 20 Pandas aren't not performing well, "generally" the other more common Pandas should suffer also. If these 20 Pandas are performing well, then "generally" the other more common Pandas should be doing well also. Of course there are performance differences with each individual coin. A> Generally speaking, if the PPI is going up, this trend should be seen throughout the Panda Market, and thus far it has been fairly accurate. Thus the PPI can be used as a marketing point on the Panda market, in much the same way, when the S&P 500 and DOW Jones Index is up, those are used as a marketing point for the stock market. I hope this helps. Side note: Since my involvement into Pandas, I have been trying to keep track of the most common 22 Pandas (1989-2011). Mainly because the top 20 are generally out of my reach. You could call this the Yennus Panda Price Index, or the Index For Poor Pandas. Those that have been to the Panda/SydneyStacker Meets have seen this chart, and what is clearly evidenced is the Panda's performance in relation to silver; and as you would expect, it's a curve very similar to PandaCollectors.