By Joseph Adinolfi, MarketWatch

30-year yield hits all-time low

NEW YORK (MarketWatch) -- The yield on the 10-year Treasury bond recorded its largest one-month decline since mid-2011, as the flow of money into bonds continued on Friday.

Typical end-of-the-month buying to match adjustments to durations in benchmark indexes combined with a weaker-than-expected reading on U.S. economic growth pushed down yield and worries about deflation in Europe to push down yields.

The yield on the 10-year Treasury slid eight basis points Friday to 1.673%, according to Tradeweb, while the yield on the 30-year Treasury hit an all-time low, down 7.5 basis points to 2.243%. Yields fall as bond prices rise.

The 10-year yield tumbled 13.5 basis points over the week, the fourth full-week drop in the last five. It plunged 49.4 basis points over January, the steepest one-month drop since August 2011, when yields plummeted 58.8 basis points.

Treasury yields have been pushing lower since the new year began, as negative yields in Europe and worries about the global economy sinking into deflation increase the appeal of U.S. debt as a haven for investors.

On Friday, those worries included the U.S. economy. Gross domestic product expanded 2.6% in the fourth quarter, down from 5% in the third quarter, according to a preliminary government estimate released by the Commerce Department. Economists surveyed by MarketWatch had predicted 3.2% growth.

That followed a provisional reading on the eurozone's rate of inflation that showed it slipped further into negative territory in January, accentuating investors' fears about deflation. The yield on the German 10-year bund closed 5.5 basis points lower to 0.301%, its lowest-ever closing yield.

The yield on the 10-year gilt -- the United Kingdom's 10-year bond -- also closed at its lowest level ever. It finished at 1.330%, down 9.1 basis points from Thursday's close.

"There's really no reason to sell bonds unless you think the [U.S.] jobs number next week is going to be very robust," said Tom di Galoma, head of rates and credit trading at ED & F Man Capital Markets.

Here's what Treasury investors were watching Friday.

Subscribe to WSJ: http://online.wsj.com?mod=djnwires