Sport England ran their fourth Active People Survey in 2010 attempting to measure how many people in England participate in various sports and whether participation has increased. Details of the survey here.
Participation in a sport was defined as the number of adults (age 16 plus) who have taken part in the sport at moderate intensity for 30 minutes or more at least once in the last week (at least four days out of the previous 28).
The survey found that Mountaineering has grown from 86,100 adults (0.21%) in 2007/8 to 111,300 adults (0.26%) in 2009/10, an increase of 25,200 participants.
Mountaineering includes: climbing indoor, climbing rock, mountaineering, mountaineering high altitude, hill trekking, hill walking, bouldering, and mountain walking.
In the period between 2007/8 (Active People Survey 2) and 2009/10 (Active People Survey 4), four sports: athletics, cycling, netball, and mountaineering show a statistically significant increase in participation rates.
You can read the full results here.
According to the BMC other indicators of mountaineering participation include:
Source: BMC News Report
As regards rock climbing several years ago UKClimbing.com asked the rock shoe distributors how many rock shoes they sold each year, the total figure was around 70,000 pairs.
Another indicator to add to the mix is UKClimbing.com's Google Analytic Figures. Google Analytics measures how many people visit UKClimbing.com and currently that is around 200,000 different people each month of which 83% are regular visitors.