Historical transaction/trade ratio. Available? Useful? Blockchain.info lists both "Trade Volume" and "Estimated Transaction Volume" in both BTC and USD. It occurred to me that the ratio of one to the other might be a useful metric in determining how much of the Bitcoin market is currently speculative versus how much is actually being used for trade.

I would be interested to see if there were, for example, a much higher trade:transaction ratio during the buildup of the bubble than in previous or current days. It might also be a useful metric for determining whether the bubble is truly over and for predicting Bubble 2.0, should one ever occur.

Does anyone know of a good historical source for this data, or perhaps have both the programming acumen and time available to create a simple graph? Or have I missed something important, economically, that makes this information less useful than I'm currently assuming it to be?
You can access the data for each currency on each exchange with the Markets API from BitcoinCharts:

For example, for USD:


http://bitcoincharts.com/charts/chart.json?m=thUSD
http://bitcoincharts.com/charts/chart.json?m=mtgoxUSD