Facebook's stock has had another down week.

It closed on Friday at $30.72, down 3.2 percent from a week ago. Since it went public in mid-May, the stock has been down for five weeks and up for three weeks. It's now 19 percent below its initial public offering price of $38.

Facebook Inc. began trading publicly in mid-May following one of the most anticipated stock offerings in history. The IPO priced at the top of a projected range that Facebook had already boosted just days earlier.

The stock had fallen sharply in the weeks following the IPO, going as low as $25.52.

Investors have been concerned about its ability to keep increasing revenue and make money from its growing mobile audience, though many analysts hold positive long-term opinions.