When I was business planning to open my store I came across some interesting statistics that I composed myself.
All of these statistics can be found Here. with the official WCA rankings. I gathered all the numbers simply by counting all rankings in the "Rubik's Cube" category up to the year and individual years. These numbers are not the exact number because some competitors have only competed in other events besides "Rubik's Cube". So I believe these are the best numbers to go by.
Below I have listed the numbers of total WCA Cubers (in red) that have competed and Active WCA Cubers(in blue) who continue to compete for each year. I also have the growth percentages for each category.
2003: 102 - N/A 89 - N/A
2004: 278 - 173% 204 - 129%
2005: 663 - 138% 515 - 152%
2006: 1,231 - 86% 818 - 59%
2007: 2,223 - 81% 1,458 - 78%
2008: 4,349 - 96% 2,935 - 101%
2009: 7,769 - 60% 4,855 - 65%
2010: 11,570 - 49% 6,005 - 24%
These numbers mean a lot of things. The biggest thing is the quick growth of WCA Speedcubing in less than a decade. Although the numbers show a somewhat decline in the growth in the last couple years, it is still growing FAST. This means we may have even more competitions and more people will compete at these events.
One thing that is notable is the difference between Total WCA cubers and Active WCA cubers. This just shows the number of people taking a break (i.e. Yu Nakajima) or those that quit from actively cubing at WCA competitions.
There are also missing numbers for the growth of speedcubing... What I have not included here are the "Non-active WCA Speedcubers". These individuals are not counted, but they are a part of the growth of this sport. Can you estimate how many Non-active WCA Speedcubers there are worldwide?
One last request from people who decide to post in this thread. Please gather the growth numbers from YOUR country (in the same manner I did). I'm quite curious what the growth is like for individual countries. Maybe we can find out which country has the highest rate of growth. Thank you!