Seven years ago management expert Peter F. Drucker wrote a book predicting that by 1985 - next year - business employees in the United States would own through their pension funds ''at least 50 - if not 60 - percent'' of the shares of American corporations.
''If 'socialism' is defined as 'ownership of the means of production by the workers' - and this is both the orthodox and the only rigorous definition - then the United States is the first truly 'Socialist' country,'' he wrote.
Well, the growth of what Mr. Drucker calls ''pension-fund socialism'' has not moved as rapidly as he anticipated, but it continues. Pensions & Investment Age magazine forecasts that the ''collectivization of the ownership'' of corporate America by pension funds and other financial institutions will be completed over the next 20 years. By the year 2000, says the trade magazine for institutional investors, more than half of the equity interest in US companies will have slipped from the hands of investors individually into the hands of investors collectively through financial institutions.
This is a quiet revolution. It has been little noticed, even by the more than 130 million Americans who own a chunk of the nation's productive enterprises through these powerful institutions.
In a telephone interview, Mr. Drucker pointed out that the growing concentration of investment power in these institutions is going to make ''more prominent'' the basic political question of control.
At the moment, corporate executives or their appointed professional managers usually make the decisions in investing an estimated $1 trillion in pension fund money (as of the end of 1982). Mr. Drucker expects trade unions and the government to battle for greater control of the concentrated financial might represented by pension funds.
''Politics abhors a vacuum,'' he noted.
In fact, there are already instances of trade unions putting pressure on pension fund managers to invest where it provides immediate jobs for their members, and not necessarily where the highest return is available.
In Sweden, the parliament last month passed controversial legislation to establish ''worker funds'' that will buy corporate stock on the open market on behalf of employees, using money taxed from companies.
Mr. Drucker says, ''I don't think we will go that way. It doesn't fit this country.''
Besides, American workers have been buying stock through their pension funds for some 50 years, a development picking up steam in recent decades. The total assets of the nation's private and state and local government pension funds reached only $17.2 billion in 1950. This total had jumped to $769.8 billion by 1980 and, considering the upturn in stock prices and continuing inflow of money, probably well exceeds $1 trillion today. Almost half of that sum is invested in common stocks.
Mr. Drucker, the Clarke professor of social science and management at Claremont Graduate School, Claremont, Calif., says that for the average person over 45 years old and with rights to a corporate pension, that pension will often be his largest single asset. (In economic terms, a right to a corporate pension or a social security pension is an asset just like ownership of a house.)
From the standpoint of corporate management, that private pension is a corporate liability. It must be paid to employees when they retire. Thus corporate executives generally want full control.
But Mr. Drucker maintains it is ''highly overdue'' that employees should have some sort of representation in the control of their pension ''property right.'' Some companies have voluntarily given employees representation in the supervision of pension funds. But this is not common.
''There has to be some way of providing accountability,'' Professor Drucker said.
Other institutions, such as mutual funds, insurance companies, banks, and even brokerage houses own large pieces of corporate America. But pension funds are the biggest institutional investors, already owning more than 20 percent of the outstanding stock of the nation's 500 largest industrial concerns.
They have even become important if not vital participants in hostile takeovers. Pension fund trustees believe they must, under the law, take advantage of the highest bid in a merger battle.
Drucker questions whether this situation is in the best national interest. Some 97 percent of companies bought out in hostile takeovers do worse financially afterward. ''The economy clearly suffers,'' Drucker said. ''It is destabilizing.''
Moreover, the managers of medium-size, rapidly growing high-technology companies are forced to manage for the short term, when they should be thinking long term. If profits drop for a quarter, the market believes the company is no longer a growth stock, he explained. The stock price falls and the company becomes ''a sitting duck for any one of 30 raiders. This dictates management behavior.''
Institutional ownership often facilitates such raids, and it concerns Mr. Drucker.
The degree of institutional ownership of pension funds will eventually stabilize. Pension funds not only accumulate assets, they sell them to pay their pensioners. But with the spread of corporate pensions and the growing proportion of senior citizens in the nation, ''pension-fund socialism'' likely has further to go and many implications. Drucker calls it ''a time bomb with a brightly burning fuse.''