Recently came across a few articles which mentioned the participation figures for the Delhi Half Marathon since its inception (21K only).
2005 - 4,000
2006 - 8,000
2007 - 10,000
2008 - 10,000
Don't yet know the quota for 2009, but whatever it is, we will get to know the "true" figures on Nov 1st, because this time, since the timing chip is compulsory for the 21K, the organizers will not be able to just give some number and expect everyone to take it as it is. Till the last year, timing results using chip were there for 1738 runners, or about 17% of total runners.
Interestingly, Mumbai marathon has a quota of 11,000 for the 21K, more than Delhi's main event!
Some useful links for results over the past years:
Results 2008
http://www.championchipuae.com/results/results.php?id=19&cat=&a...
Results 2007
http://docs.google.com/fileview?id=0B5pKeeeoEzbqMTNmOGJlMmQtOWJiYS0...
http://docs.google.com/fileview?id=0B5pKeeeoEzbqYWIwNzlkMzMtNTU1Yy0...
Results 2006
http://docs.google.com/fileview?id=0B5pKeeeoEzbqM2RlNzA5MDMtMTUzOC0...
http://docs.google.com/fileview?id=0B5pKeeeoEzbqOTk2ODU1ZWEtN2YxNC0...
Results 2005
http://www.mika.de/cms_data/hm_gender_f5caf9b1.pdf
The results for 2006 and 2007 were not actually available on the websites on which they were originally published, so I was just lucky that I had a copy of the results saved with me (in fact, the website ceased to exist).
Enjoy! And soon we will have the 2009 results too!