According to most experts, TV for kids is basically a no-no. The American Academy of Pediatrics recommends no TV at all for children under the age of 2, and for older children, one to two hours a day of educational programming at most. Various studies have linked greater amounts of television viewing to all sorts of problems, among them attention deficit disorder, violent behavior, obesity, and poor performance in school and on standardized tests. Given that kids watch an average of around four hours of TV a day, the risks would seem to be awfully high.

Most studies of the impact of television, however, are seriously flawed. They compare kids who watch TV and kids who don’t, when kids in those two groups live in very different environments. Kids who watch no TV, or only a small amount of educational programming, as a group are from much wealthier families than those who watch hours and hours. Because of their income advantage, the less-TV kids have all sorts of things going for them that have nothing to do with the impact of television. The problem with comparing them to kids who watch a lot of TV is like the problem with a study that compared, say, kids who ride to school in a Mercedes with kids who ride the bus. The data would no doubt show that Mercedes kids are more likely to score high on their SATs, go to college, and go on to high-paying jobs. None of that has anything to do with the car, but the comparison would make it look as if it did.

The only way to really know the long-term effect of TV on kids would be to run an experiment over time. But no one is going to barrage kids with TV for five years and then see if their test scores go down (though I know plenty of kids who would volunteer).

In a recent study, two economists at the University of Chicago, Matthew Gentzkow and Jesse Shapiro, came up with a different way to test the long-run impact of television on kids—by reaching back to the distant past of the information age. When Americans first started getting television in the 1940s, the availability of the medium spread across the country unevenly. Some cities, like New York, had television by 1940. Others, like Denver and Honolulu, didn’t get their first broadcasts until the early 1950s. Whenever television appeared, kids became immediate junkies: Children in households with televisions watched their boob tubes for close to four hours a day by 1950. And these programs weren’t educational—no Sesame Street or Dora the Explorer. Nor were there any real restrictions on commercials during kids’ shows (those came in the 1960s and ‘70s). There wasn’t the same level of violence on television, but in terms of kids-oriented programming, Howdy Doody was about as good as it got.

The key point for Gentzkow and Shapiro’s study is that depending on where you lived and when you were born, the total amount of TV you watched in your childhood could differ vastly. A kid born in 1947 who grew up in Denver, where the first TV station didn’t get under way until 1952, would probably not have watched much TV at all until the age of 5. But a kid born the same year in Seattle, where TV began broadcasting in 1948, could watch from the age of 1. If TV-watching during the early years damages kids’ brains, then the test scores of Denver high-school seniors in 1965 (the kids born in 1947) should be better than those of 1965 high-school seniors in Seattle.

What if you’re concerned about differences between the populations of the two cities that could affect the results? Then you compare test scores within the same city for kids born at different times. Denver kids who were in sixth grade in 1965 would have spent their whole lives with television; their 12th-grade counterparts wouldn’t have. If TV matters, the test scores of these two groups should differ, too. Think analogously about lead poisoning. Lead has been scientifically proven to damage kids’ brains. If, hypothetically, Seattle added lead to its water in 1948 and Denver did so in 1952, you would see a difference in the test-score data when the kids got to high school—the Seattle kids would score lower than the Denver kids, and the younger Denver kids would score lower than the older Denver ones, because they would have started ingesting lead at a younger age.

From the 1966 Coleman Report, the landmark study of educational opportunity commissioned by the Civil Rights Act of 1964, Gentzkow and Shapiro got 1965 test-score data for almost 300,000 kids. They looked for evidence that greater exposure to television lowered test scores. They found none. After controlling for socioeconomic status, there were no significant test-score differences between kids who lived in cities that got TV earlier as opposed to later, or between kids of pre- and post-TV-age cohorts. Nor did the kids differ significantly in the amount of homework they did, dropout rates, or the wages they eventually made. If anything, the data revealed a small positive uptick in test scores for kids who got to watch more television when they were young. For kids living in households in which English was a second language, or with a mother who had less than a high-school education, the study found that TV had a more sizable positive impact on test scores in reading and general knowledge. Evidently, Bozo the Clown was better than we remember.

So, sure, you may cringe when your kid knows every word of the Wiggles’ tune “Fruit Salad, Yummy Yummy!” That’s understandable. Watching TV has taught them many horrible songs, and for that you will suffer. But maybe you don’t need to feel too guilty about it.