Where do babies come from? Nowadays you would think that everyone knew, what with sex education so pervasive in the schools and the forces of Planned Parenthood always on the march. Yet anyone who has studied the scortatory ways of LAmerican teen-agers will tell you that the trend in teen-age pregnancy is ever upward. Despite the sex educationsts' strenuous efforts, an abundance of our kids just cannot get it right, and boy are they surprised!

It is becoming ever clearer, as Campaign '82 grows ever noisier, that the Democrats believe that a similar stubborn ignorance beclouds enough of the electorate's knowledge of economics to give the Democrats victory this fall. Where do jobs come from? Where does prosperity come from? The Democrats tell the voters that jobs come from government spending and that prosperity comes from the U.S. Treasury. They do not tell the voters where the funds for government spending come from, and they hope that the voters will not ask.

Well if the voters do ask, I suggest the Democrats answer that federal funds come from the stork. Politically speaking this is a safer answer than telling today's sorely pressed voters that the Democrats' alternative to Reaganomics is a vast jolt of federal spending, higher taxes and a return to inflation.

Right now, many Republicans are thrashing wildly to avoid the economic issue. They do not understand that in this campaign the economic issue is their issue. Not only is it clear that our present economic wobbliness is the result of the Democrats' years of stifling economic growth while engorging the federal government with ever larger chunks of the taxpayers' income; but it is also clear that the Democrats have nothing fresh to offer. Their only solution to our present condition is to raise taxes and to spend more money. That will give us what M. Mitterrand has given France, to wit: a ravening inflation and devalued currency to go along with high unemployment and economic torpor.

Last week in New York the Republican candidate for governor, Lew Lehrman, demonstrated to the nation's Republicans how the economic issue works. New York is the center of American banking and finance, management and culture. Its riches trail far back into the American past. Yet years of Democratic extravagance with high spending and high taxing have left the city and the state in pathetic economic condition. Now along comes Lehrman with an analysis and a solution. "My analysis shows that New York is no longer competitive," he affirmed last week. "Companies are fleeing the state, and others are avoiding it. The private sector has been forced to carry too heavy a load, and the state is at the bottom of the list when it comes to measuring job growth."

The problem according to Lehrman is that "the tax code of New York penalizes work, hard work and long hours. In New York, the more you work, the higher they tax you." Thus he has unveiled an eight-year program to lower the voters' personal income tax by 40 percent and halve the state's sales tax. Lehrman knows that jobs and prosperity come from enterprise and that taxes deter enterprise.

Whether Lehrman's opponent, Lt. Gov. Mario Cuomo, understands this remains unknown. His only response to Lehrman's program of tax cuts was to vapor over deficits. Cuomo's agitation over deficits is not very compelling. He never worried much about deficits in the past, and if he really is so concerned about deficits now he can cut spending.

Now in New York the fun will start. Cuomo will gasp and rend his garments over the deficits that he insists will come from Lehrman's tax cuts. Lehrman will insist deficits are not inevitable, while he pursues poor Cuomo with such questions as "How much will you raise the voters' taxes?" "How high must the cost of government become before the Democrats have brought us to the perfect society?"

Do the nation's Republicans have Lehrman's boldness? Do they have his good economic sense and enough confidence in the people's good judgment to debate the economic issue manfully in the public forum? I have no idea, but I do know that those who admire the gaudy spectacle of American politics fought out in classic style are now looking at New York's gubernatorial race. Lehrman is in hot pursuit, and Cuomo is about to begin to read from "The Grapes of Wrath" and other sad tales of capitalist infamy.