Velocity of scrollRect always returns (0.0,0.0)

In the documentation it says that ScrollRect has a velocity variable. (http://docs.unity3d.com/460/Documentation/ScriptReference/UI.ScrollRect.html)

But if I try to tap into it or output it to the console using the following code

 Debug.Log("Velocity: " + scroll.velocity.ToString());

the only output I get is

 Velocity: (0.0, 0.0)
 UnityEngine.Debug:Log(Object)

Has anyone managed to get a value from this variable? Any advice on what I might be doing wrong? Thanks in advance for any help.