Washington ? Whoever replaces Alan Greenspan as Fed chairman will have to navigate the economy through so many uncharted and dangerous waters, it’s a wonder anyone wants the job.

For starters, economic expansions become more fragile with age, and this one has never seemed very healthy from the start.

On top of that, housing prices are certainly overpriced if not in a bubble, and will be a headache whether prices keep rising or if they fall.

And no Fed chief can rest easy with energy prices at current high levels because stagflation (high inflation mixed with stagnant growth) is certainly a possibility.

Finally, looming over the economic landscape are the low U.S. savings rate and large current account deficit that are forcing economists to rewrite the textbooks.

“It could be that we have a soft landing and the new chairman comes in and says ‘wonderful’ and has a quiet period to work with,” said former Fed Gov. Lawrence Meyer.

“But there are many other alternatives here,” he said.

Federal Reserve Board Chairman Alan Greenspan poses in the Board of Governor's room in Washington in 1987, when he was appointed to the position. With Greenspan expected to retire early next year, economists and other Fed watchers are debating what defined the Greenspan era at the central bank and what his legacy will be.

“A big stack of issues could pop up,” agreed Ethan Harris, chief economist for Lehman Brothers.

At the moment, the economy appears healthy with strong job growth. The Fed has raised rates steadily to the current 3.5 percent from 1 percent in June 2004, and has signaled that it plans to continue with a measured pace of increases.

But some economists are worried that the Fed will tighten too much and hurt the economy. The risks increase if the new chairman focuses on inflation like a laser beam to establish his or her inflation-fighting credibility.

The first tough question for the new chairman could be how much more to tighten in the current cycle and, more fundamentally, what is the acceptable rate of inflation.

“On the tightening cycle, they have a real decision to make,” said John Silvia, chief economist at Wachovia Securities.

Will the Fed allow the economy to continue to grow at its current 3.75 percent rate, or would that engender inflation over time?

There is a chance the Fed’s steady rate hikes this year could trigger a severe slowdown in housing prices, leading to a quite “significant slowdown” in 2006, Meyer said.

Another pressing concern is oil prices, which have stayed higher for longer than economists had forecast. While the economy seems to be on solid footing despite the high price of gasoline, economists are worried it may eventually disrupt economic growth and fuel inflation – a period of so-called stagflation, a troubling economic condition that combines the worst of both worlds and defies easy solutions.

Federal Reserve Chairman Alan Greenspan testifies in March before the Senate Special Aging Committee about retirement economics. With Greenspan expected to retire early next year, economists and other Fed watchers are debating who might be tapped to fill his seat.

What happens next in the housing market also is uncharted territory, economists said.

Outright property depreciation is rare unless there is general economic decline, said Richard DeKaser, chief economist at National City.

Looming over the economic landscape is the fact that the United States is the largest debtor nation and has an insatiable appetite for foreign goods.

What troubles economists is the possibility of a sharp correction to the U.S. exchange rate if there is a loss of confidence.

“You are never quite sure at what point the markets might start to move against you pretty darn quickly,” said Silvia of Wachovia.

Economists in Europe and Japan believe the United States must increase its savings rate, which would only lower U.S. gross domestic product.

Former Fed Gov. Meyer said it was amazing how little is known about the current account deficit.

“The kind of things we tend to teach in the classroom” don’t have much relevance to the current situation, Meyer said.

Mark Zandi, chief economist at Economy.com, said the next Fed chairman will have to learn how to conduct monetary policy in coordination with the European Central Bank and the Peoples Bank of China.

Greenspan was able to make monetary policy without much regard for the other central banks, he said.

“It’s really been a one-economy show and 10 years from now it won’t be,” Zandi said.