Japan’s 20- and 30-year bond yields dropped to record lows as the U.K.’s decision to leave the European Union reinforced demand for the haven of government debt.

Yields are likely to stay low after the shock of so-called Brexit subsides, bond investors said at a regular meeting with Japan’s Ministry of Finance in Tokyo Monday, according to an official who spoke on condition of anonymity in line with policy. They also said that while Japanese bonds have become slightly expensive, any increase in yields will probably attract buyers, the official said.

Japan’s 20-year bond yield fell three basis points to 0.085 percent as of 4:10 p.m. in Tokyo from Friday, after touching a record low of 0.08 percent, according to Japan Bond Trading Co. The price rose 0.599 yen to 102.258. The 30-year yield declined 3 1/2 basis points to an unprecedented 0.11 percent.

It’s getting harder to invest as yields decline on domestic bonds and hedging costs increase for foreign debt, some investors said at the meeting, according to the MOF official.

Cross-currency basis swap spreads showed the cost to borrow dollars in exchange for yen reached 68 basis points on Friday, the highest since November 2011. The benchmark 10-year U.S. Treasury yield reached an almost four-year low of 1.4 percent on Friday.

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