You might not be able to learn exactly how many BTCs are used on goods and services, but you might be able to get the next best thing, assuming the major BTC exchange public keys are known.
A metric of the number of transactions and the amount transferred with the major BTC exchanges compared to the number of transactions total would be useful. You could probably pull that off the block chain, right? We could assume that the transactions not on the major exchanges would mostly be private exchanges for goods and services and transfers of money between individual's accounts for purposes of things like secure backup, right? ...
Thanks bubblesort. That sounds like a good idea to start with. I know that at the blockchain.info site (
http://blockchain.info/charts) there are charts on estimated transaction volume as well as exchange traded volume, so the data looks to be there. I also note there is a chart of the Trade Volume v Transaction Volume Ratio, but its specification makes it very jumpy and difficult to interpret. Something along the lines of Transaction Volume less Trade Volume might perhaps be more insightful. If you know a way of extracting this numerical data, I am all ears. Cheers.
I still think some fundamental spending trend data, if any exists, would do a lot to inform the investor base and give more confidence for a broader range of potential merchants to participate. So if anybody else has ideas, keep them coming. Thanks.