I know sometimes there is a debate about whether it's exploitative to give incentives. One project I've been involved in, we're tracking youth across time, and especially when foster youth get to be 17, 18 and then we're also following them as they leave the system, this is a highly mobile group. Sometimes the only connection we can have with them is 'If we can interview you again a year from now, you'll receive $50 or a $50 gift certificate.' They're not going to want to be involved just for the sake of research, so we need to keep them motivated. It's very important.