Today's edition of Washington Business begins the second year for a tabloid section of The Washington Post that was something of a gamble this time last year.

The editors of The Post had concluded that more coverage of local and regional business, consumer and economic issues was warranted because of the growth of the private sector and investment activity in an area long dominated by government. But there was some concern about readership on Mondays -- traditionally a day when newspapers have carried little business news.

Starting with the first issue, however, it was evident from telephone conversations and letters that Washington Business would have a big audience. c

According to the annual report of The Washington Post Co., in a discussion of its newspaper operations, "the biggest single news inovation in 1980 was the launching of Washington Business . . . in addition to providing extensive new coverage of the area economic scene for Post readers, the section was an immediate hit with advertisers. Advertising revenues from this new section topped estimates by more than 120 percent."

Determined not to rest on such laurels, we thought it would be appropriate in our first birthday issue to invite all of the newspaper's readers to share with us their ideas about the strengths and shortcomings of Washington Business.

We have lots of ideas about what we want to include in the section as it expands, but it will be a more valuable and useful publication if your suggestions are added, too.

On this page there is a brief questionnaire. We invite you to send your comments to Washington Business, at the address listed.

It is appropriate for The Post to seek readers' reactions and ideas on this section, in particular because many regular features now included are in response to suggestions by readers in earlier years.

Our goal from the beginning of Washington Business has been to provide all our readers with more complete reporting and statistical information about the local community and investment issues, as a complement to The Post's daily and Sunday business sections. Now it's your turn to tell us how we're doing. a

One of the features Washington Business introduced was the Economic Index, designed to monitor the overall health of the metropolitian area's economy.

Like any indicator based as much as possible on the most recent statistics, the weekly index in this section should be recognized for what it is -- a guide to trends and not a scientific product. To compile an absolutely accurate barometer, one would have to wait for years to pass before all of the data was in.

Some of the statistics used to compile the index are available only on a monthly, quarterly or yearly basis. Most of the data reflect activity several weeks ago, at the earliest, by the time it is available. The data come from a variety of sources, including research by The Post, private companies and trade associations and the local or federal governments.

There are shortcomings to this index, one of the most notable being the absence of up-to-date area retail sales information. This is important because retail-wholesale trade is metropolitan Washington's largest single business sector, employing 303,000 area residents (the broad services industry and professions employ 428,700 persons overall, but that includes many sectors such as accounting, medicine, law, consulting and hotels).

Currently, we rely on U.S. Commerce Department retail sales estimates, which often are several months behind the cash registers. For example, retail sales data for January were published by the government only last week, showing a substantial 13 percent increase in January to $1.3 billion compared with $1.15 billion during the same month last year. Nationwide in January, sales were up 10 percent.

The Greater Washington Board of Trade does compile area retail sales figures on a weekly basis, but that organization turned down a formal request from The Washington Post for access total sales figures for inclusion in the Washington Business index. So the area's retailers have a dubious advantage over the rest of the public by knowing weeks before the rest of us how well local stores are doing.

Given such caveats, the local index remains a useful tool. It will be refined and made as accurate as possible as new information is made available.

For the past year, the index appears to have tracked local economic trends fairly closely. Starting at 102.9 a year ago, the index now stands at 105.9, for a very modest growth of about 3 percent. Local employment, for example, was up about 4 percent in 1980.

There were substantial declines in some economic sectors here over the past 12 months, particularly real estate, and the index itself declined in the spring of 1980 as record interest rates shut down some construction, postponed auto and house sales and ate into spendable income. The index also declined during several subsequent periods.

On the whole, however, the local economy did not suffer a recession as employment remained abnormally stable and personal income continued to expand. Although local retailers had expected the worst during an election year, the total volume of business at area stores was strong, up 12 percent for the year to a record $15.3 billion. Since the retail figures include automobile sales, the non-auto sector gains were even greater than the data indicate.

Among other local indicators showing gains for the year, the Johnston, Lemon & Co. Inc. index of 30 area stocks is up sharply to record levels, the volume of checks cleared by D.C. banks continues to rise, and office-industrial vacancy rates remain minimal.

On the weak side, besides construction, the Conference Board index of newspaper help-wanted ads (a particularly sensitive indicator of hiring trends) is down from a year ago but not as bad as the lowest levels of 1980, while airport passenger business is down by a significant margin, reflecting much higher fares.

Finally, area consumer prices rose by 10.9 percent in the past year, mainly because of housing, energy and food prices. More than any other factor, the inflation held back what otherwise would have been a banner year here.

In next week's editions of Washington Business, we will publish The Washington Post's annual directory of the largest area business enterprises. The 1981 list has been expanded to include 100 firms or quasi-government corporations, up from 60 in previous years. CAPTION:

Illustration, no caption, By John Pack for The Washington Post; Graph, Washington Business Regional Economic Index For The Year Ended 13 April 1981 By Glenn Mosser -- The Washington Post