Longer term rates, on the other hand, are constrained by the expectation that inflation will remain very low in 2018.

Rick Rieder, global chief investment officer of Fixed Income at BlackRock, says inflation could surprise the market next year. It is possible that a falling unemployment rate at a time of solid economic growth could put ample pressure on wages that would, in turn, raise inflation off the floor. “I think we can get to 2 percent,” Mr. Rieder said. The Federal Reserve’s preferred inflation measure has crawled along below 1.5 percent since the financial crisis.

A 2 percent inflation rate would most likely just nudge long-term rates higher, he said, adding that he expects a “slow and low trajectory” for long-term rates. His base case is that the 10-year Treasury rate, now at about 2.5 percent, won’t rise much beyond 2.7 percent.

Unless inflation surges unexpectedly, a 3 percent yield for the 10-year Treasury note may not be likely. Julien Scholnick, a fixed income manager at Western Asset Management, which manages $435 billion in global bond portfolios, notes that a year ago, the 10-year Treasury bill rose briefly to 2.6 percent. And that was after the surprise election of Donald J. Trump spurred an expectation of quick stimulus materializing through tax changes, infrastructure spending and regulatory easing.

“We don’t see higher inflation as probable,” in 2018, Mr. Scholnick said. With an expectation that long-term rates will not venture far from current levels, the Western Asset Core Plus Bond fund currently has an average duration — a measure of risk to changing interest rates — that is slightly higher than the six-year norm for the benchmark Bloomberg Barclays U.S. Aggregate Bond index.

Shifting economic and market dynamics in 2018 may raise the value of small tweaks to basic bond portfolios.

The high-quality United States bonds in the aggregate bond index will deliver on their main purpose in your 401(k): When stocks falter, these bonds will hold their ground, and they may even rally. But the aggregate index will also be very sensitive to Federal Reserve interest rate increases, as 37 percent of the index is invested in Treasuries and another 27 percent in government agency bonds.