The yield on 30-year Treasury bonds sank to a more than one-year low Wednesday, as collapsing yields in Europe prompted investors to reach for higher-yielding U.S. government debt.

An auction of $35 billion in five-year notes drew the highest demand in 13 months from an investor class including foreign central banks as the debt yielded the most over its German equivalent in almost nine years. Federal Reserve Chair Janet Yellen said last week that U.S. interest rates may rise from zero sooner than policy makers estimate on labor markets gains, while weaker data in Europe is spurring speculation the European Central Bank will consider quantitative easing.

“The rally is being led by what’s going on in Europe and the bond markets there,” said Charles Comiskey, New York-based head of Treasury trading at Bank of Nova Scotia in New York, one of 22 primary dealers that are obligated to bid in U.S. debt auctions. “The Fed is in play, so you’d best be out the curve a bit in the seven- to 10-year sector, as long as there are no hiccups with inflation.”

Yields on 30-year bonds dropped five basis points to 3.11 percent at 3:07 p.m. New York time, according to Bloomberg Bond Trader data, and touched 3.10 percent, the lowest level since May 22, 2013. The 3.125 percent bond maturing in August 2044 rose 1 3/32, or $10.94 per $1,000 face amount, to 100 12/32.

The benchmark 10-year note's yield dropped four basis points, or 0.04 percentage point, to 2.36 percent, the least since Aug. 18. Two-year note yields rose two basis points to 0.52 percent, narrowing the difference, or spread, between two- and 10-year yields to the least in more than a year.

European Yields

European debt yields plunged to record lows after ECB President Mario Draghi said on Aug. 22 that bets on price increases in the currency bloc “exhibited significant declines.” Policy makers hold their next rate-setting meeting on Sept. 4.

Spanish 10-year yields fell three basis points to 2.15 percent, after reaching 2.083 percent, the lowest since Bloomberg began tracking the data in 1993. The rate on Italy’s debt declined to as low as 2.343 percent, while that on French bonds slid to 1.228 percent, both records. German yields dropped to less than 0.9 percent for the first time, while those on Austrian, Belgian, Dutch, Finnish, Irish debt also fell to lows.

‘Flattening Trend’

U.S. five-year notes yielded 146 basis points, or nearly 1 1/2 percentage points, more than their German equivalent after widening to 148 basis points on Monday, the most since November 2005. Treasurys yielded 79 basis points more than their G-7 counterparts, the widest since June 2007.

“Some investors in Europe are buying Treasurys to seek better yields because of the economic and Fed’s policy outlook,” said Alessandro Giansanti, a senior rates strategist at ING Groep NV in Amsterdam. “The Treasury curve is likely to maintain its flattening trend amid speculation the Fed is heading for a tighter policy.”

Yellen’s comments made in Jackson Hole, Wyo., last week added to speculation the central bank is preparing to boost interest rates next year. The majority of Fed officials predict the central bank will start raising borrowing costs in 2015 based on forecasts it published in June.

Traders saw about a 54 percent chance the Fed will increase its benchmark rate from the current range of zero to 0.25 percent by July 2015, according to futures data compiled by Bloomberg.

‘Fantastic Auction’

The five-year notes sold Wednesday yielded 1.646 percent, compared with a forecast of 1.645 percent in a Bloomberg News survey of six of the Federal Reserve’s 22 primary dealers.

Indirect bidders, which includes foreign central banks, purchased 52.7 percent of the notes, compared with an average of 46.4 percent for the past 10 sales and the most since July 2013.

The bid-to-cover ratio, which gauges demand by comparing total bids with the amount of securities offered, was 2.81, versus an average of 2.73 for the past 10 sales.

“It was a fantastic auction,” said Ray Remy, head of fixed income in New York at Daiwa Capital Markets America Inc., one of 22 primary dealers obligated to bid at U.S. auctions. “What’s driving the U.S. Treasury market is what’s going on in Europe. As Europe moves to lower yields, money is moving into the U.S. Treasury market to take advantage of the bigger spread between the two.”

Week’s Sales

The U.S. also sold $13 billion of two-year floating notes at a high discount margin of 0.055 percent, below the 0.07 percent last month. The securities drew bids for 4.38 times the amount available, versus 4.09 times the July 30 sale and a 4.73 average over the eight offerings of the notes since they were introduced in January.

The U.S. is scheduled to sell $29 billion of seven-year securities Thursday. Tuesday’s two-year sale drew a yield of 0.53 percent, compared with 0.544 percent at the previous auction of the securities in July, which was the highest since May 2011.

The spread between the two- and 10-year note yields fell to as low as 185 basis points Wednesday, the least since June 2013. A yield curve is a chart showing rates on bonds of different maturities, with a flatter curve suggesting some investors expect short-term interest rates to rise.

The butterfly spread formed by two-, five- and 10-year Treasury yields was 39 basis points, almost the the highest since August 2009. It has averaged 9.2 basis points over the past year. A higher reading signals investors are more bearish on the middle of the three securities, making it relatively cheap versus the others.