(Bloomberg) -- Investors are clamoring to buy the one kind of security that few companies want to sell now: long-dated bonds.

When blue-chip companies have sold debt maturing in 30 years or more in the US, they've found heavy demand, with money managers placing orders equal to about five times the notes for sale on average. That ratio is higher than in any other period dating back to 2021.

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Drugmaker Eli Lilly & Co drew $14.7 billion of orders earlier this week for just $2 billion of 30- and 40-year bonds. Investors are eager to lock in yields above 5.5%, a relatively high level, especially as money managers enjoy robust inflows and the Federal Reserve gets closer to cutting rates.

"Being able to buy high quality investment-grade credit near 5% is something that for a long time was not available," said David Brown, global co-head of investment grade at Neuberger Berman. "People are trying to lock in these rates."

Companies, meanwhile, are reluctant to commit to paying elevated coupons for decades by selling debt with far-out maturities, and a quiet market for acquisitions has limited the supply of offerings. Those dynamics have spurred even more of a frenzy for the long-term debt that is available.

Heightened demand has compressed spreads in the secondary market. Bonds with 10 or more years of duration have seen risk premiums narrow 6 basis points this year through Thursday's close, while shorter- and intermediate-dated bonds have narrowed just 2 basis points.

"Anything in the longer end of the maturity curve right now is being met with substantial, outsized demand since investors are incentivized to put their money to work in a higher rate environment, in an under-supplied part of the market," said Jiyann Daemi, head of US corporate syndicate at TD Securities.

Some companies this year have turned to Europe for their long borrowing needs, where yields are lower. In February, Johnson & Johnson sold 30-year paper there but securities only as long as 10 years in the US, while in May Pfizer Inc. issued 20-year bonds in Europe.

For bonds with at least 10 years of duration, investors are getting a yield of 5.75%, more than a percentage point higher than the 10-year average, a Bloomberg index shows. Yields have been relatively high for longer maturities for several years, but demand this year has been even more pronounced because money managers lately have had plenty of capital to put to work.