JP,
The data is said to be negatively skewed, which is to be expected given the nature of the survey and it is clear to me that each data range is not cumulative.
Have a look at this https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/458432/how-people-travel-cycling.pdf which shows, half way down on LHS, that 35% of population of England (53 million) of ages 5+ cycle at least annually. Extrapolating this across the population of the UK (64 million) indicates a total in excess of 22 million who cycle at least annually. Then add in the younger kids who cycle.
Why is this figure so hard to believe?
Here's a radical suggestion * (not one to which I subscribe and which I write with a degree of irony). Get some old paint and mark out a line little wider than a shoe along the worst bits of the towpath, really tight up to the hedge where all the rubbish, broken glass and mouldy dog turds lie. Chasten those walkers that dare to stray outside this line, perhaps aided by the use of garroting wires. We can call this a dedicated walking path! Encourage all pedestrians on the walking path to wear hi-viz, a helmet, lights and a cow-bell around their necks. Then we can blame any walker that is struck down and injured by a careless cyclist when outside the walking path. To pay for this magnificent infrastructure we can charge walkers to use the walking path. Problem solved!
* (These are all topics raised by others on this thread alone, modified to suit the above senario)
No, actually I still think it better to treat all towpath users with consideration and respect.