Women's liberation and economic hard times are influencing more American wives to remain childless, perhaps establishing a record, the government reports. In a report on childbearing trends based on data gathered in the late 1970s, the Census Bureau says the American birth rate continues to decline. It is now measured at 2.2 children per family, just a point above the "zero-growth" rate of 2.1 children per family that prevails in Japan and many European countries. The government researchers say they don't know if the decline is permanent. But the report says some demographers speculate that if current low fertility rates continue, the proportion of American women completing their childbearing years without children could reach a record 25 to 30 percent. The highest proportion of childless wives so far recorded is 22 percent, and that occured around the turn of the century. The Census Bureau cites interweaving social and economic patterns to acocunt for the decline in the birth rate. "While the increase in childlessness among young women is due, in part, to the economic uncertainties faced by young couples today," the report says, "recent changes can also be traced to the attitudes of young wives toward early childbearing and the pursuit of their own educational and career goals." With the arrival of what the Census Bureau calls the "modern contraceptive period" of the late 1960s and 1970s, only 30 percent of women of childbearing age had their first baby by the age of 21.

But the latest data also show that very few women -- only 7.4 percent -- wait until the age of 30 or older to have their first child. And of all babies born, less than 3 percent are those of women in their early 30s. None of this holds true, incidentally, for American women if Hispanic origin. Of all the children born to women 18 to 44 years old in a sample year in the late 1970's, 10 percent were born to Hispanic women although they constituted only 6 percent of all women in the age group.