US workers in the dark on options for retirement. THE PENSION GAP

Yet another deficiency has surfaced in America's troubled system of private pensions. Most of the 25 million Americans with pensions do not even know when they are eligible to retire. Pollster Louis Harris, who has done several studies on aging, calls this latest finding ``nothing short of shocking.''

It raises ``serious questions,'' says Prof. Merton C. Bernstein, ``whether those with such vague knowledge of retirement-plan provisions can make adequate plans for retirement.'' This is of particular concern because an increasing number of Americans have been actively participating in their retirement plans in recent years through contributions to tax-deferred savings plans. Mr. Bernstein is a professor of law at Washington University in St. Louis and co-author of a forthcoming book on social security. He was principal consultant to the 1982 National Commission on Social Security Reform.

Bernstein says the majority of Americans with retirement plans elect to retire early. But if they do not even know the age at which they are eligible, are they likely to have an understanding of the more-complex benefit issues posed by complicated benefit plans? he asks.

For several years pensions have been under sharp scrutiny in Washington. Although Congress has taken several recent steps to improve pensions, major concerns remain: Half of all working Americans have none; many plans are considered inadequate; and the stability of existing programs is suspect.

The General Accounting Office reports that 41 percent of Americans in pension plans that permit early retirement do not know when they are eligible to retire with benefits. Further, 72 percent don't know at what age they can retire with full benefits.

``Under federal law,'' pollster Harris told a congressional hearing Wednesday, employers are supposed to let their employees know such basic facts about pension plans. ``It is obvious that either the companies have been remiss in their legal duties, or the employees have ignored the information,'' he said.

Rep. Edward R. Roybal (D) of California says this ``alarming'' information should ``alert the Congress and the federal agencies ... that more is needed in the way of public education and enforcement [of current pension law] to ensure that workers are adequately apprised and can exercise their pension rights.'' Mr. Roybal chairs the House Select Committee on Aging, which held the hearings.

Today some 900,000 pension plans exist in the United States. But they cover only about half of all American workers, and that percentage has been declining for a decade and a half.

Further, many jobs created in recent years have been in small companies that offer no pensions or plans les generous than those of large employers.

Since 1985 three large US companies have closed several pension plans: Allis-Chalmers Corporation, Wheeling-Pittsburgh Steel Corporation, and LTV Corporation.

These well-publicized episodes have made many workers uneasy about the security of their pensions, even though the federal Pension Benefit Guaranty Corporation took over the liabilities and made payments to these companies' pensioners.