The tenth anniversary of 9/11 initiated many interesting articles on al Qaeda. The Wall Street Journal published "Shadowy Figure: al Qaeda's size is hard to measure". Following this lead, I launched a crowdsourcing effort a month ago to determine al Qaeda's size based on the estimates provided by those visiting this blog. This question, unlike my past surveys, should have been well suited for crowdsourcing (I'll explain why I believe this in a separate post in the coming weeks.)

In total 54 respondents answered the question "How many people in the entire world are members of al Qaeda?" and collectively arrived at the following estimates for the number of al Qaeda members globally.

--3,448 people are in al Qaeda - according to the average of all responses.

or

--1,300 people are in al Qaeda - according to the median response of all responses.

and

--5,000 people are in al Qaeda - was the most common response - the mode.

Personally, I thought some outlying responses made the average too high and the median (middle response of all responses) a bit more realistic. The mode response of 5,000 didn't surprise me as I've commonly heard the numbers 1,000, 5,000 and 10,000 thrown out in news stories related to al Qaeda.

Overall, the highest estimate was 100,000,000 (an outlier I removed since it skewed all the results). The second highest estimate was 25,000 and cast by a 'Private Sector' voter. The lowest estimate was 100 and cast by a 'Other' category voter. Here is the breakdown for each professional group's average estimate of the size of al Qaeda.

Military (including defense contractors) = 5,306
Government (Non-military) = 912
Private Sector = 6738
Academia = 2830
Other Voters = 1413

While I don't know this, I wonder if 'Private Sector' voters estimate higher because they watch more television news on al Qaeda? I've always felt news coverage made al Qaeda feel bigger than they are in reality.

I'm most interested in the 'Government - Non Military' voters. The estimate of the nine voters selecting this professional category is substantially lower than the other groups.

For more analysis see here.
And for related surveys see here.