Babies cost $50,000 to $100,000 to rear in the current U.S. economy, and within 20 years will be so expensive that they could become status symbols, somewhat like private airplanes, a Temple University demographer believes. "Dollars and diapers will be signs of the good life," says Dr. Joseph McFalls Jr. Noneconomic factors are reinforcing the trend, he adds. Changing social mores mean women are more likely to work while making it acceptable to have few or no children. Marriages often end in divorce, and, of course, birth control is widespread. "For fertility to rise, all these things must reverse, and what's the likelihood of that?" he asks. "If you look at the fertility trend over the last 200 years, the baby boom was the only significant interruption in the long decline of fertility." In fact, he says, the U.S. fertility rate has already fallen to 1.8 children per couple, meaning that parents are not replacing themselves. By the year 2000, as many as a third of all individuals will choose childlessness, he believes. One former reason for large families -- the search for a child of particular sex -- will also soon end, he says. "The new technology will make it possible for the parents to achieve this through two pregnancies." Meanwhile, the Wilson Quarterly in its summer issue charts what it costs to bring up a child born to middle-class parents in a city in the North Central states in 1961. The list assumes not more than four siblings and that the child attends public schools. It excludes the cost of childbirth in a hospital (estimated at $1,050 in 1961), the cost of a college education ($5,000 a year at a state university in 1979 when this child would have entered) and the loss of income to the mother for bearing and rearing the child (for a first child this is assumed to be about the same as the maintenance costs, in this case $36,110).