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.
Updating schemes. The blue filled circles denote the end of each week and the implementation of the weekly updating algorithm. The arrows show the history of data used in each scheme. Week 1, in all cases, is not considered in the process, and it is only used to obtain an initial estimate of the parameters.
