HOW SECURE is that private pension you may be counting on for your declining years? Fortunately, most people can feel relatively sanguine, provided they don't lose or switch jobs too often. Private plans are again increasing in number, and-- thanks to good management, high interest returns and funding requirements put into law in 1974-- most of them are in good financial shape.

Some plans with relatively large enrollments may be headed for trouble. Federal, state and local government plans are not covered by the requirements of the 1974 Employee Retirement Income Security Act (add ERISA to your acronym vocabulary), and some with generous benefits and early retirement face large future deficits.

Private-sector plans in potential trouble are typically those in declining industries. Even with ERISA's requirements, uncovered obligations can pile up when employers agree to increase promised benefit levels but don't build up the necessary reserves to cover the added costs of pension credits already earned by workers. If the companies keep growing, they can continue to cover retirement payments, but if employment starts to sag--watch out!

If worse comes to worse and a company fails entirely, the Pension Benefit Guaranty Corporation (acronym it PBGC) will step in to pay off uncovered retirement obligations. PBGC is seeking--and needs--a substantial increase in premiums paid by insured companies. Another needed safeguard is to close loopholes in current law that allow companies to dump their pension liabilities on the government even though they are not in danger of going out of business. A company would have to turn over 30 percent of its assets to PBGC--or spin off its liabilities into a subsidiary company--but this might be a good deal for companies that are feeling pressure from ERISA's funding requirements.

Raising the premium and closing these loopholes would put PBGC on a solid basis for the foreseeable future--unless the economy suffers from a rash of big bankruptcies like the recent Braniff failure. Even then, the insurance corporation wouldn't be in trouble right away because it would also fall heir to the assets in the failed pension plans, which it could use to cover payments for some time.

Continued serious economic trouble would put many private pensions in trouble--along with much else. There is also good reason for some companies --and governments--to look seriously at the future costs of the benefits they are promising, and begin negotiating more reasonable terms for future workers. By and large, however, the pension outlook is promising--at least for the lucky worker with a stable job in a profitable concern.