During the market’s steep decline last year, OTCBB volume dropped in half from approximately 1.3 billion shares a month to only 585 million. Since February, however, interest in the OTCBB market has continued to build. Last month, a total of 1.5 billion shares were traded.

Detailed data can be found at following link: http://www.otcbb.com/dynamic/tradingdata/sharedollarvolume/dollardata.htm