User demographics

[Westech]

One of my sites was just passed over for contract with a very big advertiser. I think that one of the reasons for this might have been my inability to provide demographic data about my user's ages. I was able to provide all of the other information this advertiser asked for: uniques, pageviews, countries, languages, etc., but I have absolutely no data about our user's ages.

How do websites generally collect this information? A survey on the site would seem to be the obvious answer, but I think that this would be horribly inaccurate. Certain age groups would be more likely to skip the survey or enter incorrect information than other age groups thus skewing the results.

Does anyone have any suggestions on how to accurately gather age demographic data?

[Kings]

Surveys are really the only way possible, and I can't think of any other way. Most big websites that seem to use surveys have had success with it, and BURST! does it as well (or did? haven't used them for a while).

[Chris]

Burst still uses them.

[Cutter]

Do a pop-under, pop-up, or embed a survey into your site. If you can provide some incentive for them to submit, that would be ideal. You can also estimate your age group by looking at similar sites.

[s2kinteg916]

I see alot of sites just run random polls for demographics...