Enrollment in the U.S.-funded Medicare plans run by UnitedHealth Group Inc. (UNH), Humana Inc. and other insurers may rise 50 percent in the next decade rather than declining as predicted earlier, U.S. budget analysts said. Medicare Advantage plans for the elderly and disabled will swell to 21 million participants by fiscal 2023 from 14 million this year, the Congressional Budget Office said yesterday in its annual review of the federal budget. The CBO didn't explain the revision from its previous estimate that enrollment would fall to 11 million and a spokeswoman didn't respond to an e-mail.