In a holiday season when the wolf is more likely to be at the door than reindeer, the Season's Greetings card is an important economic indicator.

A careful reading of the approximately 10,000 card designs of the 3 billion expected to be sent this year is, according to some observers at least, as reliable as the consumer price index in predicting the mood of the country.

Madonna and child, churches in the snow, choir boys, menorahs, mangers and African votive objects are popular this year. For a decade or so, there was little interest in religious cards. But now, Hallmark says religious cards make up 30 percent of its stock. American Artists Group figures 22 percent of its cards have religious themes.

The National Gallery of Art, the Library of Congress and the Metropolitan Museum lead in reproducing the old master religious pictures. This year, the National Gallery has reproduced fewer oil paintings, but has added two new black-ink-on-antique-white drawings, one a Nativity scene by Albrecht Durer.

Architect Ted Naos, Washington's own maker of elegant die-cut cards sold in museums across the country -- he sold 80,000 cards last year -- added two more religious cards to his 28 designs this year in response to the demand. But he's sold more of his Christmas tree cutout this year, perhaps because it becomes a tree ornament.

More cards this year are geared to specific religions. UNICEF, which offers the greatest variety of languages, religions and ethnic motifs, has many cards based on Hebrew symbols, several with Torah covers, including one intricate decoration from 16th-century Romania.

The Library of Congress has a card showing a late 19th-century Shiviti Plaque from Hebron and an articulation diagram by Baron Franciscus Mercurius van Helmont (circa 1667) for the first four letters of the Hebrew alphabet for teaching lip reading. Several handsome UNICEF cards carry glittering gold motifs of African religious symbols such as a "soul bearer" shield and a gold mask.

The American Artists Group cards include more than eight with peace dove designs.

Most of the rest portray global unity, including a handsome embossed card with a world in the center of circling planets. A card by Heidi Brandt carries a plea for "peace on earth to all turtles, elephants, whales, egrets, snail darters, lions, eagles, black-footed ferrets, kangaroos, koala bears, timber wolves, Hawaiian tree snails, California redwoods, quetzal birds, polar bears and pandas, seals and all the other endangered species such as you and me and us." The Phillips Collection, which didn't sell cards last year, has made a Peaceable Kingdom" card from an Edward Hicks painting.

The blacker side of the thought is seen in a series of cards by Jest Expressions of Silver Spring. Secretary of the Interior James Watt is shown on one of the cards in front of a wall full of mounted Santa's reindeer heads.

Children are returning to Season's Greetings cards. The American Artists Group expects children to play on even more cards in 1983. The National Gallery, in an early expression of the theme, has a black-and-white drawing of anatomically correct nude boys by Heinrich Aldegrever.

Washington cards are selling especially well here. The Corcoran Gallery of Art finds its own cards, a photo by Lelia G. Hendren that shows the Corcoran lion with a wreath around its neck and line drawings of the Old Executive Office Building and the Capitol, are selling very well. Garfinckel's Dorethe Whitehead, the stationery buyer who designs cards, has drawings of the Capitol, Fairfax and Georgetown by Barbara Noel Deiso of Crofton that are hot sellers.

Nostalgia, which began to be a popular theme in the early '70s, is also returning for a replay. "Snow at Louveciennes," by Alfred Sisley, is the best seller at the Phillips Collection. Whitehead says red and green cards are the most popular in her shop. The British cards, no doubt reflecting "Brideshead Revisited," are full of teddy bears.

Cards are quieter, less assertive this year.Colors vary between traditional and drippily wishy-washy. Sentiments are proper.

Cards always respond to the cultural climate. In the 1960s, cards were filled with Significance. Peace doves, peace signs, one-world symbols, love-thy-neighbor, save the whales, the last flower in the world, and other peaceable kingdom and environmental motifs were popular on recycled paper. Earth and sky colors were in vogue.

In the 1970s, the Me-Me-Me and Oh, You Kid generation took over. Following Richard Nixon and Watergate, cynicism was rife. Even Santa was suspect. He was seen on cards riding a snowmobile, playing tennis, cavorting in bars with blonds, skiing, in general having a good time, while heaven knows what was happening to the reindeer, not to mention Christmas.Colors were brighter, brasher. Graphics were super.

With the election of Jimmy Carter, things began to wind down. All that talk about being born again and the religious revival was reflected in an increase in religious cards.

Last year, Congress stole Christmas from the card sellers and makers by raising stamp prices. Card-sending, which had declined a bit anyway, went down further. So in this recession year, according to Gary Smith, executive vice president of the National Association of Greeting Card Publishers, the card makers expected the worse and made fewer cards. The retailers ordered less. Apparently, about a week or so ago, people got the Christmas spirit and rediscovered the Greeting Card.

A number of explanations have been put forth as to why:

In a year of high unemployment, people are renewing old contacts with friends, relatives and anyone who might help them find another job if they need one.

With money scarce, people who once sent presents are sending cards. People who once telephoned are choosing the cheaper method of writing cards.

With more people at home, willingly or not, there's more leisure to write cards.

As Noah sent out the dove to find out if the world was still there, so people are sending out cards to check on their friends. Smith puts it this way: "We've had a sort of siege mentality: the hostages, the recession, the unemployment rate, the wars and rumors of wars. Some people send out cards as a question, saying, 'I'm okay. Are you okay?" CAPTION: Illustration 1, Copyright (c) Misterpiece Studios Inc.; Illustration 2, Courtesy of Library of Congress