(Bloomberg News) Investors have pushed sales of structured notes tied to interest rates and commodities up almost 40 percent on concern that inflation may rise, making them the fastest-growing types of offerings in 2011.

Issuance has increased to $6.35 billion in the U.S. in the first five months from $4.56 billion a year earlier, according to data compiled by Bloomberg from prospectuses filed with the U.S. Securities and Exchange Commission. Equity-tied securities gained at less than half that pace, or 17 percent, to $10.1 billion.

The notes are being purchased as protection against inflation, said Justin Capetola, who helps manage about $300 million as a partner at Blue Bell Private Wealth Management, a fee-based advisory firm in Blue Bell, Pennsylvania.

"Investors are concerned that the dollar is going to be worth less and less," Capetola said in a telephone interview. "So there's been more interest in rate- and commodity-linked notes."

Sales of commodity-tied notes rose to $2.27 billion in the first five months, while the Standard & Poor's GSCI Index, an index of 24 raw materials, increased 12 percent, Bloomberg data show. Rate-linked notes climbed to $4.08 billion.

Bank of America Corp., the biggest seller of structured notes in the U.S., issued $60.9 million of 18-month notes tied to the price of oil on May 25. Investors receive twice the gains in crude oil futures, capped at 44 percent annually, with the risk of losing all of their principal, according to a prospectus filed with the SEC.

JPMorgan Notes

JPMorgan Chase & Co. issued $71.2 million of 10-year, fixed-to-floating-rate notes linked to the consumer price index. The bonds pay 4 percent interest annually for two years, then switch to the 12-month difference of the CPI plus 2 percent, with the total capped at 8 percent, according to a prospectus filed with the SEC.

Structured notes are securities created by banks, which package debt with derivatives to offer customized bets to investors while earning fees and raising money. Derivatives are contracts whose value is derived from stocks, bonds, currencies and commodities.