Because of the money it lavishes on its automobiles, the average American family has reached the point of spending more money on transportation than on food.

It also is putting proportionately less money into food on the family table and more into meals in restaurants.

These revesals of family spending priorities are recorded in a survey of 20,000 families conducted by the Bureau of Labor Statistics. If its findings could be sketched into one neat picture, it would portray the typical family piling into an expensive car for a quick trip to the local fastfood emporium.

It shows that the proportion of family expenditures that went for food in 1972-73 was 20.1 per cent as compared with 24.4 per cent in 1960-61, when the last BLS survey was undertaken.

The trend was just the reverse for transportation. In 1960, the average family put 15.2 per cent of its expenditures into transportation. That share increased to 21.4 per cent in 1972.

The survey showed up a few other spending habits. Booze is down, for example. The share spent on alcoholic beverages declined slightly - from 1.5 to 1.4 per cent in the 1960s. (The BLS has discovered, over the years, that people lie about how much money they spend for booze: they habitually report spending 50 per cent less than they actually do.)

And there's not much satisfaction in the statistics for companies that sell books, magazines, and newspapers. The proportion of family expenditures that went for reading materials declined, from 0.9 to 0.6 per cent.

It was clearly the automobile - big, fast, expensive and lavishly equipped - that caused the big shift in spending priorities during the decade.

For one thing, people bought more cars, says Eva Jacobs, chief of the BLS Division of Living Condition Studies. The survey found that the average family had 1.3 cars in 1972, compared with 1.0 a decade earlier.

They were also buying more expensive cars. It wasn't just that auto prices went up, which they did. More important, statistically at least, was the American preference for larger, more lavish, cars. It doesn't show up in the survey, but Jacobs says retail sales data show the average car bought in 1972 was double that of 1960 in cost.

Whatever the reason, the typical family back in 1960 spent $693 to buy, maintain, and fuel the automobile. In 1972, the average expenditure had increased to $1,566, and that was before the price of fuel started its rise in 1973.

Although the proportion spent on food declined, that doesn't mean the American family wasn't eating as much or as well. For one thing, the size of the family was declining (from 3.2 persons to 2.9 in the period covered by the two surveys) and so there were fewer stomachs to fill.

There's also another reason: There is a kind of upper limit to what a family can spend on food. It can only eat so much. And although incomes rise, as they did during that period, the amount needed for meals usually stays fairly stable or rises only slightly. The result is that food preempts a declining portion of the money available.

There is confirmation in the survey of the fears of supermarkets that more of the family food dollar is going to restaurants, less for homecooked meals. Between 1960 and 1972, the proportion of expenditures that went for food used at home declined from 19.6 per cent to 14 per cent - the biggest change recorded by the survey. In the same period, the proportion that went for "food away from home" increased slightly, from 4.9 per cent to 6 per cent. The fast-food franchises drew much of this money away from the supermarkets, it is thought.

The other family expenses showed minor changes. Housing increased from 28.4 to 31.4 per cent of total spending. Clothing expenses declined, and so did spending for recreation personal care and education.

And the proportion spent on utility bills stayed the same, at 4.9 per cent. But that was before the energy crisissent electric, fuel oil and gas bills spiralling upward.