according to The Search Agency's Mobile Experience Scorecard
Research from The Search Agency shows that “9 of the  web-only [retail] companies used RWD”. That's 91 percent not using Responsive Web Design.
Greg Sterling writing for Marketing Land analyses the research and outlines the performance benefits of dedicated mobile web sites. Here's just one of the charts he presents.
I believe so strongly in the power of the web server to optimise performance, particularly when handling mobile devices, and give better online experiences I founded 51Degrees. As such it's always nice to read independent research supporting these sound engineering principles.
Many of the 1.5 million web sites using 51Degrees utilise both REsponsive Server Side (RESS) techniques alongside RWD to provide improved web sites. A few of them even analysis goal conversions by screen size and input method to work out how they can continuously optimise for an ever increasing range of devices.