Parents, do you know where your teen-ager is spending the money tonight?

I was listening to the news on my car radio the other day and one of the items was about teen-age spending.

As I remember, it said that teen-agers spent $40 billion of their parents’ money in 1986, and $30.5 billion of their own. Much of the $40 billion was spent for groceries by teen-agers who had to do the shopping for working parents.

The study was made by Teenage Research Unlimited, and its figures were derived from questionnaires sent to 5,000 teen-agers.

Many of the respondents said they not only selected the family’s groceries but also chose the magazines that came into the home.

Where did the teen-agers get the $30.5 billion that was their own money? Did they have jobs? Or was it from their allowances? It said they spent a lot of their own money on electronic musical equipment and videotapes.

Of course, since we’re living in a $3-trillion economy, $40 billion isn’t a lot of money. Yet I would think that it is enough to attract the eye of manufacturers and purveyors of groceries, and to influence the variety of products they offer.

If teen-agers are left to do the family shopping, our national diet must be sliding toward pizzas, hamburgers, ice cream, frozen enchiladas, Pepsi, Coke, 7-Up and Mountain Dew.

It seems to me that parents who are already so overtaxed by 9-to-5 jobs that they don’t have time to do the grocery shopping need more than a teen-age diet to sustain life and health.

It’s an ominous trend.

I remember reading not so long ago that the teen-age influence on American consumer goods and taste was declining, as our teen-agers matured into yuppies. It was welcome news, even though it meant that for years we would be submerged in yuppie tastes; but this new survey seems to evaporate even that limited optimism.

We’ve known for years that our movies were being made for teen-agers, and we have sort of accommodated to that by retrogressing in our minds and tastes to a teen-age level. There’s an adolescent in each of us, and when it rises we can appreciate such testimonials to the loss of innocence as “Private School,” “Puberty Blues,” “Valley Girl,” “Losin’ It,” “Risky Business” “Sex Kittens Go to College,” “Teen Wolf,” “Fast Times at Ridgemont High” and others too numerous and too embarrassing to mention.

If teen-agers have $70 billion to spend, there isn’t much chance for relief from this kind of entertainment. On the other hand, TV programming for “adults” is so banal that I have sought escape by tuning in on most of the pictures named above. That I may have suffered a certain mental retardation as a result of this fare I readily concede.

I suppose that deep down, my reaction to these astounding statistics is one of belated envy. When I was a teen-ager you could go on a spending spree for $2; a $10 bill would buy the family’s groceries for a week. I could go downtown on Saturday and take in two double-feature movies, a hamburger and a malted milk for 80 cents.

If you were taking a girl to a prom, the staggering part of the expense was the gardenia corsage, which could set you back as much as 75 cents, but it was mandatory. You stopped by a florist and picked it up, then rang the girl’s doorbell and when she opened the door, you shoved the gardenia at her, wrapped in its sheet of waxed green paper, and said, “Here.” She squealed and pinned it to the shoulder of her dress, and you spent the evening inhaling its aphrodisiac fumes.

Afterward you took her to a drive-in where you appeased her more socially acceptable hungers with a hamburger and a malt, for 30 cents, and left her at her door, far short of having accomplished or even attempted to accomplish your ultimate fantasy goal.

As for buying the family groceries, I was sometimes sent out in the night to the nearby ma-and-pa grocery for some urgently needed item, but I hardly was allowed to do the shopping.

My most acute memory of the Depression is of being given a $10 bill by my sister to buy a pound of hamburger, which was 15 cents a pound, and returning home with change for $1, not $10. In superbly controlled anxiety she sent me back to get the remaining $9 in change. I had little hope the butcher would surrender it. It was a disaster of life-crushing proportion. My sister made $25 a week singing on the radio, and was supporting both me and my mother. To my indescribable relief, the butcher found the $10 bill in his $1 bill drawer and cheerfully paid me back my $9--with a sort of tenderness, as if he knew he was saving my life.

Of course it is sheer nostalgic nonsense to wonder at the buying power of $1 in 1933, since incomes were commensurate with the prices of those days. Even so, in an absolute sense we were much poorer than teen-agers of today. We had little spending money; we had little clothing; we might have owned a phonograph and a few Bing Crosby records, if our parents were wealthy.

Movies not only didn’t give the impression that teen-agers engaged in sex, they gave the impression that nobody engaged in sex.

And there’s one thing we surely didn’t do--we didn’t decide what our family was going to read or what it was going to have for dinner.