Updating the Employee Referral Bonus Program

I've always been a big proponent of paying employees a referral bonus since the quality of employees you get from staff referrals is usually higher than when you rely on people just walking in off the street.  I've always believed that you shouldn't pay the referral bonus until the new employee reached his/her 90th day. 

I recently read an article from the restaurant industry pointing out that in today's instant gratification world the three-month wait for a payout may no longer be enough to motivate employees. 

I think they have a point. Almost every company I talk to feels that their referral program isn't used as much as they would like it to be. I've come around to a new position on this.  I would pay 50% of the bonus when the referred person is hired and the other 50% when they make their 90 days.