From what I can gather these are the correct figures.
apparently 67,000 people are expected to be affected by the benefit cap whether working part time or out of work.
http://www.bbc.co.uk/news/mobile/uk-politics-16675314 looks like figures have been revised upwards frm 50,000 to 67,000
1 in 8 people on housing benefit are unemployed
approx 2.5 million people are on JSA
if we times this by 8 to get the total number of people on benefits of some sort this adds up to 20 million.
Dividing 20 million by 67,000 we get 298.5 which means that 1/298.5 of people will be affected by the benefit cap or 0.00335%
To get a more accurate figure of those of working age affected I have doubled that amount as half of the people in receipt of housing benefit are OAPs resulting in 0.0067% - and then doubled it again as the cap applies per household and many people live as couples - this reaches the figure of 0.0134% - so this is a definate over estimation.
As such - those affected by the benefit cap are in an extreme minority and therefore in exceptional circumstances.
To put this in context - a couple living together in my area without children would receive approx £10,000 between them ie for their household - thats adding up JSA, Housing Benefit and Council Tax Benefit and thats if they are over 35 - if they are under 35 it would be less.