Sign-on bonuses and relocation benefits

I'm looking for repayment practices on sign-on bonuses and relocation benefits. I realize they can be hard to collect, but we don't want to give these benefits away in the event someone departs within a year.
Thank you to all who responded to the survey question. There were 20 responses:

• 16 say 100% repayment if leave within a year (3 of these say if leave within 2 years pro-rata amount due back)
• 4 have a variable schedule based on dollar amount/position level
• Additionally a good majority describe the bonus as an earned item that is not wholly earned until month 12 even though is paid in month 1. Various companies utilize specific forms to address the repayment issue, in addition to wording in the offer letter.