Take a look at the market share graph (2010 to 2013) in the Investor Pres of July 2015. IM and DickerData/ED have the same market share. Since then, I dare say that DD would have beaten them (although ED did drop some vendors that they were doubling up on).
Can I ask which particular product set(s) you are looking at?
DDR Price at posting:
$1.80 Sentiment: Buy Disclosure: Held
A personalised tool to help users track selected stocks. Delivering real-time notifications on price updates, announcements, and performance stats on each to help make informed investment decisions.
(20min delay)