Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Interval between 1st and 2nd evaluation: < 12 months (circles), 12–48 months (triangles), > 48 months (squares). Horizontal lines = median values.
