So the problem with USD volume is when the price of BTS goes from 0.88 to 0.22; USD volume falls by 75% as well. And just to be clear I have seen scam coins have a volume of 10% of the daily volume (IE it looks like there is $45 million of volume but $5 million is a scam coin so that number is off 10%.) Transactions are just as easy to fake as volume numbers. (it is all done by computers...). When it works there are some real nice charts on the cryptofresh site.