Another sigal this time the monthly report on industrial production -- adds to the evidence that the economy has slowed down a little. Only temporarily? That still seems probable. But, taken with the rise in unemployment last month, the production figures clearly show that the economy has been going through a deceleration. American industrial production is a little lower now than at the beginning of the year.

One reason is, apparently, that the adverse effects of the drop in oil prices have hit the economy much faster than the benefits. The domestic oil industry has cut its drilling programs drastically, with an immediate impact on all the companies that provide and operate oil field equipment. That has had particularly severe repercussions because the oil fields are often in the same regions as wheat fields, where communities were already struggling to cope with the farmers' distress. The high oil and grain prices of the 1970s drew wealth from the two coasts to the center of the country. That pattern has now reversed itself with a vengeance. In time other businesses will react to the tonic of cheaper fuel. But so far that's only beginning to happen.

There are other causes of the slowdown. Both businesses and consumers are cautious about the kind of large purchases that can be postponed. Automobile production has been erratic all year. The output of business equipment and household appliances is down. And another thing: production of defense and space equipment is no longer rising. Boosting the economy is the worst of reasons for increasing the defense budget. But as defense spending levels off, there will be no further push from a stimulant that has affected the economy powerfully in recent years.

By a coincidence, unwelcome but instructive, the figures showing the drop in production appeared on the same day as other figures showing a blip upward in producers' prices. A single month's data don't necessarily set a trend. But the producers' prices had been falling steadily since the end of last year, and the sudden jump in May is at least a reminder that inflation's recent good behavior ought not be taken for granted. The two statistics, taken together, narrow the choices ahead for the Reagan administration and the Federal Reserve Board. The remedies for slow economic growth will increase the risk of higher inflation, and vice versa.