The stock is evaluated by a private organization whose methodology is not explicitly released AFAIK.
That may be true but its profits and sales grew from year to year. Its not like they said, now our stock is worth 30 dollars a share. They are still audited and have to play by the SEC rules.
Publix made a 1 dollar jump in stock prices this last quarter. For a privately held grocery store to do that, they have to be doing something right. Especially with the economy how it is and the increase in Wal mart grocery stores and the even cheaper Aldi grocery stores moving in.