The Fed is expected to raise interest rates again at its meeting on Wednesday, which has almost been digested by financial markets, but do not expect the meeting to be "calm". Some investment bank analysts believe that the Fed may still surprise the market at Yellen's "farewell meeting".

Many strategists and economists expect the Fed to leave interest rate expectations unchanged, but there is reason to think that Fed officials may acknowledge that the tax bill could trigger a stimulus that would change their outlook for GDP and interest rates.

One argument against this view is that this is Janet Yellen's last meeting as Fed chairman, and the Fed is likely to maintain the status quo during this transition period until Jerome Powell Powell becomes chairman early next year.

Jim Caron, portfolio manager and fixed income strategist at Morgan Stanley Investment Management Company (Morgan Stanley Investment Management), said the Fed's interpretation of the impact of tax reform could surprise the market. The Fed had expected to raise interest rates three times in 2018, but will the tax reform increase the Fed's expectation of raising interest rates to four times next year?

Caron believes that the threshold for raising the expected number of rate hikes to four is very low. This is really something that investors need to pay attention to.

Even before Ms Yellen leaves, the Fed's composition has changed, and voting committees will change next year, and the market expects the Fed to be slightly hawkish next year.

"I really don't think so, but they could be surprising," Caron said. The Fed may acknowledge the small boost to economic growth from the tax cuts, but it should not have much impact on the economy as a whole.

If the Fed does change interest rate expectations, Ms Yellen will have to explain it in a press release. Caron said he did not expect interest rate expectations to change and there would be no surprises in Ms Yellen's speech.

However, Seth Carpenter, chief US economist at UBS, takes a different view, believing that the Fed may raise its forecast for interest rate increases to four in 2018 instead of the current three.

The Carpenter said that with the US House of Representatives and Senate working on an ultimate tax reform bill, there was more reason for the Fed to raise its GDP growth forecast slightly. He predicts that the tax reform plan will increase GDP by 0.25 percent a year over the next few years.

"I think they can change his GDP forecasts, and they may also change their inflation forecasts," Carpenter said. They may also change their expectations of raising interest rates three times in 2018.

Michael Gapen, chief US economist at Barclays, said he expected the Fed to stick to its expectations of three rate hikes, but some officials may raise their personal forecasts to four.

Gapen pointed out that concerns about low inflation may cause some Fed officials to maintain their expectations of raising interest rates two or three times, but the more they prefer fiscal stimulus, the more likely individual officials are to raise their expectations of raising interest rates to four times.

Gapen said he thought what would happen would be a "slight rise in GDP", although he guessed that "inflation will look the same, which should support a modest adjustment in the interest rate path."

Gapen has raised its forecast for the Fed to raise interest rates next year and now expects to raise interest rates three times instead of the previous two, mainly based on falling unemployment and the imminent arrival of Powell.

Barclays economists now expect the fed to raise interest rates in march, June and December, respectively, leaving the federal funds rate at 2.25% by the end of next year. Tax cuts are likely to start affecting economic activity in 2018, which could lead to a faster rate-raising cycle for the Fed if economic activity improves.

Gapen said the Fed's comments are unlikely to provide more new information, and Ms. Yellen is unlikely to say much at a news conference.