> We get an annual newsletter highlighting recent publications from the study, periodic random $20 checks after phone surveys, and -- oddly -- packages with bir

> We get an annual newsletter highlighting recent publications from the study, periodic random $20 checks after phone surveys, and -- oddly -- packages with birthday cards, holiday greetings, and small toys or coloring books every few months. I guess this is how you keep people active in longitudinal studies? Wild. This makes me want to see a longitudinal study on the difference in outcomes between people who participate in longitudinal studies and those who don't...