An advantage of having central clearing is that you can get reliable trading volume data. (tradingsetupsreview.com)
To find out, I looked up data on ETFs introduced before 2008 by iShares and Claymore and obtained the average trading volume data from the TSX website. (canadiancapitalist.com)
We took a brief look at the recent trading volume data (you can access this data here) published by one of the largest discount brokerage firms in the US, Interactive Brokers (ticker symbol IBKR). (sparxtrading.com)