"If it is foreign interest, it is very consistent with what I've been told by our clients in Asia. People literally say they can't put cash to work fast enough. There's a number of portfolios that are limited to conservative fixed income investments," he said. Compared to U.K. gilts, JGBs and Bunds, the yields in the U.S. would look good.
Strategists have been expecting the long end of the Treasury curve to stay depressed by the low yields in other parts of the world, but the short end could move higher when the Fed gets closer to raising rates. Rjavinski said investors he visited in Asia see one rate hike this year as already priced into the market.
"If you just look at fundamentals, it should probably be higher," he said of the 10-year yield. His year-end target is a yield of 2.02 percent.
Robert Tipp, chief investment officer and head of global bonds at Prudential Fixed Income, said the 10-year yield could stay in the 1.25 to 2.25 percent range for the next year and a half.
"It's a pretty damp squib world, and the U.S. is part of that," he said. He said it is unlikely the U.S. will join Europe and Japan with negative yields.
"The fact of the matter is, economies are not overheating. If economies were overheating and inflation was rising, there would be a belief this was an environment that would bring us to an end of negative yields, but all we're seeing is the world needs negative yields in order to have respectable growth," he said.
As for negative yields, he said the liquidity is helping to support the market. "I think though one area of danger is to the extent that negative yields are hurting the financial system," he said. "That could create some risk that could create strains in markets."
Some traders have said the move into Bunds was also the effect of concerns about Brexit, the U.K. vote on whether to leave the European Union. Tipp said that June 23 vote is the nearest risk to markets.
Paulsen said the bond markets appear more "manipulated" than ever by central banks. Telling is the fact that U.S. yields keep slipping, as if in a flight to quality, while corporate spreads are narrowing.
"The story might be if we make a run and breach a new high in stocks, will bonds finally respond?" he said.