THE INFLATION RATE is slowly coming down. The trend is clear, despite the bad bounce in the Consumer Price Index for July. It's the trend that you need to keep in mind, as you form a judgment about the Reagan administration's campaign to stabilize prices.

Inflaction hit its most recent peak around the turn of the year -- just before or just after, depending on which way you choose to measure it. Last winter it was between 10 percent and 12 percent. Now it's around 8 percent. Will this trend continue, under the double pressure of the tax cuts that become effection on Oct. 1 and the coming rise in defense spending? That's very much an open question. But the progress over the past half-year is unargualbe.

Since the Consumer Price Index jumps around from month to month, statisticians try to track an underlying rate.That's an attempt to look beyond the current increase in a price to the way in which society responds to it, absorbing it or passing it on in other wage and price increases. One approach is to follow people's earnings, since the basis mechanism that perpetuates inflation is the cycle of price increases that justify wage increases that they justify further price increases. The Labor Department has just published its Employment Compensation Index for the three months of April through June, and that number deserves attention.

Unlike most earnings statistics, it includes the fringe benefits that -- particularly because they are tax-free -- have risen much faster than cash wages and salaries. The figures show the compensation was increasing far less rapidly through the spring than last winter, or at any time during the previous year.

Most Americans seem to be under the impression that the country's standards of living have been declining over the past year, because wages were falling behind inflated prices. That's not quite accurate. Particularly if you take the fringe benefits into account, you will find that Americans' average earnings have stayed well ahead of prices. Instead of taking all their pay in cash and using some of it to pay doctors' bills, people now take some of their pay in the form of medical insurance. They take some of it in pension rights, and life insurance, and so forth. Those things aren't picked up in the conventional earnings statistics, but they are an important and growing part of most people's pay -- and they contribute to their standards of living just as straight cash does.

The decline in inflation over the first half of this year is owed partly to good luck, and partly to good management. Oil prices have fallen a little. tFood prices were stable, although that may now be changing. The government, for its part, has tightly restrained the money supply, keeping interest rates very high. That has been a major contribution to the lower inflation rates. But has the government been squeezing too hard on money, creating too much social distress? You can't prove it yet. Unemployment fell a little this summer, and earnings are still rising faster than prices.