The end of this week brings a milestone of special interest to economy-watchers in the United States: The last government statistical report of 1988.

The numbers, due out Friday on an index designed to gauge the future course of the economy, are expected to show ambiguous results - supporting neither those who think business activity is growing too fast nor those who fear an impending recession.That seems only fitting as the capper on a year in which monthly economic statistics became a fixation in the financial markets and elsewhere, but yielded up no agreement on what the figures all meant.

Analysts at the investment firm of Smith Barney, Harris Upham & Co. say Friday's report on the index of leading economic indicators for November will show a modest decline of perhaps 0.2 percent.

That would follow a small rise in October (subject to revision in Friday's report), a decline in September and an increase in August.

Plus, minus, plus, minus - the official barometer of the economic weather is promising something on the order of "clear to partly cloudy with a chance of rain or snow."

Of course the flow of numbers won't stop with the arrival of the new year. Indeed, it will be nearly spring before all the last data have been gathered on the waning stages of 1988.

By then, stock and bond traders, business analysts and other interested parties will be closely scrutinizing the statistics to get a feel for how 1989 has begun.

But if the hue and cry over each individual number will probably continue, there is the hope at least that people will come to view the figures in a more favorable light.

"If all else is forgotten, 1988 should be remembered as the year that all news was bad news," said Jay Donnaruma, an analyst at First Albany Corp. in Albany, N.Y. "The better the economy did, the more the markets worried."

What would it take to dispel this seemingly perverse pessimism in the months ahead? The prescription many analysts offer runs something like this:

-President-elect George Bush makes some decisive proposals to narrow the federal budget deficit and gets an unexpectedly upbeat response from Congress.

-Economic reports get more consistent and show an unmistakable slowing in economic growth to a pace that looks as if it can last for a long time.

-The Federal Reserve, seeing this, relaxes its tight grip on the reins of credit policy, allowing interest rates to decline.

-Lower rates help the stock market to rally with a vigor not seen since before the crash of 1987.

Altogether, that's a lot to wish for, especially without some bumps along the way.

The bond market, which determines the level of many kinds of interest rates, swerved up or down a half dozen times in 1988, notes Maury Harris, economist at PaineWebber Inc.

"In 1989," he says, "perceptions will undoubtedly continue to shift many times, but in an anticipated environment of slower economic growth."

The statistics-watchers who help create these sudden shifts in the perception of the outlook are a much-despised lot. In their preoccupation with short-term numbers, it is widely agreed, they lose sight of the thing that matters most - the long-term direction of the economy.

Still, they may serve a useful purpose. After all, by tradition the ultimate threat to economic health is complacency. And the figure-followers never sit still long enough to stop worrying.