My website is 100% https. I have links to other http domains. The referrer header is not set when linking from a https page to a http page. From http://en.wikipedia.org/wiki/HTTP_referrer

If a website is accessed from a HTTP Secure (HTTPS) connection and a link points to anywhere except another secure location, then the referer field is not sent.

I would prefer that other domains can see the referrer so that they know that traffic comes from my domain. Is there a way to force this header or is there another solution?

Update

I've done some basic testing using a redirect:

http page  -- link to http  --> 301 redirect --> http page = referrer intact
https page -- link to https --> 301 redirect --> http page = referrer blank
https page -- link to http  --> 301 redirect --> http page = referrer blank
https page -- link to http  --> 302 redirect --> http page = referrer blank

The referrer is lost when linking from a https page to a http redirect page on my own domain. So there is no referrer on the redirect.