Tick tock - more info.

Back in January I mentioned the idea of a game clock for football matches - a clock which measures actual play time, so there would be no point in dilly-dallying about taking that goal kick or throw-in because the clock wouldn't start running again until you did put the ball back in to play.  The question I left in the air was - how long should a match governed by a game clock last?  Well I came across an American site recently which has done some research on this and found that in football (soccer) you get about 33 minutes actual play for every hour that passes.   So that would suggest a game clock match should last about 25 minutes each way.  It is of course an American site but I can't imagine their matches differ much from ours.  The statistic on that site which really did surprise me is that in tennis according to them you only get about 10 minutes actual action per hour!