According to an article in silicon.com titled “IT Helpdesks suffering user password hell” (login as guest and search for the article):

Up to 80 per cent of calls received by helpdesk staff are from end users who’ve forgotten their passwords - and with each support call costing organisations around £15, the problem is not as trivial as it may sound.

Yes, it’s a UK study. The study goes on to conclude that what’s required is a fast system for resetting passwords. I maintain that what’s required is better authentication techniques, such as smart-card based keypairs. Sadly, while we’ve had the technology commercially available for more than a decade, we still can’t get vendors to use it.