Nine million Soviet workers have just obtained a wage increase of 18 per cent, and they have done it without a single strike, without a cross word passing between labor and management. They didn't even have to ask for it. How was it done?

The wage increase was pre-ordained by the five-year plan, under which 31 million workers were to get more pay in 1976-80. It is all done in orderly stages, with the more deserving categories of workers coming first. It is the Kremlin, of course, that decides which are the more deserving categories.

A year ago the wage increase went to the most deserving of all: those who work in the harsh climate of the extreme north, the far east and Siberia - the areas that find it most difficult to recruit labor. The present increase applies to the industrial centers of the Ural mountains, to Central Asia and the Volga region. The next increase, presumably in a year's time, will go to the rest of the European part of the Soviet Union, where living and working conditions are generally better.

The gap between those who earn most and those who earn least is no longer as large as it was under Stalin. At a conference on Soviet labor problems held recently at the George Kennan Institute for Advanced Russian Studies in Washington, some speakers were even heard to ask whether the gap had not been reduced too much. The experts agree that the narrowing of the gap is due to increase for the workers in the lower-paid categories. The salaries of managerial personnel have remained at the same level for a number of years.

But the top management is part of the Soviet new class, and its members are often entitled to privileges that the worker can only dream about. With the increase that goes into effect this month, the average wage will be 155 rubles a month. The salaries of top managers could be three or four times as high. But they also receive additional bonuses, which are far more substantial than those given to workers.

The perquisites of office include chauffered limousines, better housing, country dachas, access to special shops with scarce goods not available to the ordinary worker and, in some cases, a free monthly food ration for the officeholder's family. No one can be sure about the real value of the "perks," because all information about the special distribution network for the privileged class is treated as a state secret. Nothing is ever said about it in the Soviet press. But some observers believe that the circle of people entitled to such privileges has been narrowing steadily since the death of Stalin.

If the trend toward reducing the gap in money incomes continues, will the manager's salary provide him with sufficient incentives to increase productivity and efficiency? Some Western economists argue that technological advance, on which the economic progress of the modern state depends, requires the managers to be willing to take risks. Most people are risk-averters rather than risk-takers. If they have a sure chance of winning $1,000 but only a 50 per cent of chance of winning $2,000, they would choose the first rather than the second.

This is assumed to be true also of Soviet managers. To induce managers to take the greater risks, one usually has to pay them more. Greater equality of income, these economists argue, would discourage risk-taking and would thus tend to slow down the already sluggish rate of technological progress in the Soviet Union. On the other hand, if the Kremlin were to change the direction of its incomes policy and were to increase the gap between the workers and their bosses, it could be storing up political trouble for itself.

The Soviet working class has shown little interest so far in the dissident movement, partly because it has seen a constant improvement in its standard of living since the death of Stalin. It still has a long way to go before it catches up with the standard of living in the West, but this is politically less important. So long as most Soviet workers are prevented from traveling abroad, they cannot make indivious comparisions.

What the Soviet worker can see is the difference between his own standard of living and that of his bosses - just as the Western worker can see it. But the Western worker is conditioned to accept the difference as an inevitable and necessary element of the capitalist system. The Soviet worker, on the other hand, is taught to believe that full material equality is possible and desirable. He is told that this is what the Soviet Union is working toward, even as he is given an elaborate theoretical explanation why the attainment of this ideal state will have to take some time.

The Soviet leaders are working to reduce the income differentials because they believe in the just society and want to bring it closer - but also because they know that Soviet workers would not remain docile for long in the absence of visible improvement. There is scattered but increasing evidence of their dissatisfaction with working conditions.

Something close to industrial unrest is beginning to take shape in the Soviet Union. From this it could be but a step to political dissent. The wage increases are welcome, but the 31 million workers who are scheduled to receive them during the current five-year plan compose only a third of the work force. Some of the others may have to wait much longer, and they may not always be willing to do so.