Our follow-up rates were pretty good. We just finished the 14 years study and we're a little bit down. But even so, for a longitudinal study for 14 years, I think that's extremely good. We got 96% at birth; about 4% moved out of the city. We are currently in the middle of our 16 year study and it's getting a little more problematic because the kids can now say "no" as well as the moms. The flip-side of that is that kids can come in without the moms.