Traders say investors are becoming more reluctant to invest in mortgage securities and other riskier assets as yearend approaches, and spreads are holding steady as a result.

For example, the difference in yield between Fannie Mae 6% pass-throughs for January delivery and 8.5-year Treasuries on Wednesday afternoon was little changed from early Tuesday, at 173 basis points.

"The yearend is coming up, and investors are trying to lock in performance," said Jeff Given, an investment analyst at John Hancock Advisors in Boston.

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