Busy day for the folks over at FXCM (NYSE:FXCM). The leading retail forex broker reported it somewhat bucked the trend of down volumes in May, with retail FX volume metrics rising 5% from April, coming in at $263 billion for the month (see chart below).

Institutional volumes were flat at $185 billion.

In a more interesting development, an SEC filing shows that investment manager William Blair & Co. has become the largest institutional shareholder in FXCM, with a 10.38% stake. Note that William Blair's holding is in the publicly traded Common shares – FXCM has a separate series of private shares held only by insiders, so fully diluted William Blair would hold less than 5% of FXCM.