Returns on catastrophe bonds are exceeding those on corporate debt by the most in nine months as investors facing record-low yields chase returns detached from economic performance.

The bonds, designed to protect insurers from payouts on natural disasters such as hurricanes, have gained 1 percent this month, compared with a loss of 0.9 percent for company debt, according to the Swiss Re Cat Bond Total Return index and Bank of America Merrill Lynch data. Returns on dollar-denominated cat bonds were half those of corporates in 2011 as an earthquake and nuclear accident in Japan sparked record losses.

Issuance in the $15 billion market for catastrophe bonds is growing at the fastest pace in five years as investors seek securities that don't depend on payrolls growth in the U.S. or a solution to Europe's sovereign-debt crisis. An average yield of about 9 percentage points more than short-term lending rates compares with 5.89 percentage points on junk bonds in the U.S.