In the winter of 1947, Howard Head, an aerospace engineer, was skiing down Stowe Mountain when he decided that wooden skis were a terrible idea. He kept tripping on the long hickory blades; the material was too heavy for such a nimble sport. On the train back to Baltimore, Head began sketching out a new ski made out of airplane parts, focusing on the aluminum alloys and plastic laminates used to construct the fuselage. It took a few more years of stubborn tinkering—Head’s first 45 prototypes came apart on the slopes—but by the 1960s his aerospace skis were dominating at the Olympics.

In 1972, Head sold his skiing company and settled into retirement. To stay in shape, Head started taking tennis lessons. However, he soon realized that he wasn’t very good at the game; his shots careened all over the court. Head could have practiced more, but that didn’t seem very fun, so he decided to fix the tennis racket instead. At the time, virtually all rackets were made of wood, with an elliptical surface area of roughly 70 inches. While companies had experimented with slightly larger rackets—more surface area meant a bigger sweet spot—they were ultimately constrained by the weight of wood.

Head’s insight, which he laid out in a 1974 patent application, was that new materials could eliminate these tradeoffs. Head settled on a composite blend of carbon fiber and resin, which allowed him to create a racket with 40 percent more surface area and a far larger sweet spot. The end result was a piece of equipment that made the game much easier for amateurs.

Screen Shot 2018-04-16 at 9.15.37 AM.png

In 1978, Head got one of his new oversized rackets into the hands of a talented 16-year old named Pam Shriver. Although Shriver entered the U.S. Open unseeded, she ended up beating Martina Navratilova in the semifinals. Pros took notice: by 1984, composite rackets had taken over the tour. (John McEnroe was the last player to win a major tournament with a wooden racket, beating Bjorn Borg at the 1981 U.S. Open.) You can see the triumph of composites in this chart:

Screen Shot 2018-04-18 at 2.05.38 PM.png

This is a portrait of technological disruption. As such, the game of tennis in the post-composite age provides an ideal case-study with which to investigate the impact of innovation. That, at least, is the premise of a new working paper by the economists Ian Fillmore and Jonathan Hall. By looking at every men’s professional tennis match played between 1968 and 2014, Fillmore and Hall were able to map out the unlikely impact of Howard Head’s invention.

The first thing they found is that composite rackets dramatically shifted the demographics of the pro tour. In the mid-1970s, when wooden rackets still dominated, nearly 20 percent of all matches featured a player above the age of 30. By 1990, that number had shrunk to roughly 5 percent of matches.

The youngest players made up the difference. Between 1975 and 1984, the percentage of matches involving players under the age of 21 nearly tripled, to 30 percent.

Why were composite rackets so hard on the oldest players? Head, after all, invented the composite racket to help old guys like himself hit good shots; it was supposed to level the playing field. And yet, his invention ended up doing the exact opposite, tilting the competitive balance in favor of youth.

To understand how this happened, it’s important to look at how composite rackets were actually used on the pro tour. While Howard Head was trying to create a bigger sweet spot for amateurs, professionals didn’t really need a bigger sweet spot. Instead, they used these new rackets to give their shots more topspin. As noted by the physicist Rod Cross, the best players using wooden rackets were only able to impart a topspin of about 200 rpm on a typical forehand. However, the increased width of the composite racket meant that players could attack the ball at a more extreme angle, and thus generate 1000 rpm of topspin. That’s a five-fold increase in ball rotation, which allowed them to hit with more velocity, and to create higher bounces that are harder to return. (Just imagine the consequences for baseball if pitchers invented a breaking ball with five times more spin. The home run would soon become a relic.)

What does topspin have to do with older players? To take full advantage of Head’s innovation, experienced players had to quickly learn a new set of tactics and techniques. They had to change their grips, stances, and swings to maximize spin. Interestingly, the increased experience of veterans seemed to interfere with this adjustment, which is why their exit rate from the tour doubled between 1970 and 1984. Head invented the composite racket to make it easier for older players like himself to hit good shots. He ended up ridding the pro tour of nearly everyone over 30, at least for a generation of players.

There’s a larger lesson here: when it comes to technological disruption, we inevitably fail to anticipate the real-world consequences. The public sphere is lousy with pundits and prophets, boldly forecasting the future impact of the latest technology. Winners, losers, etc. But what history teaches us is that nobody knows anything.

In their paper on tennis, Fillmore and Hall briefly reference the impact of photography on modern painting as another example of how technology disrupts in unpredictable ways. After J.M.W. Turner saw a daguerreotype for the first time, he declared: “This is the end of art. I am glad I have had my day.” Turner saw the photograph as a dire competitive threat, since it meant everyone could engage in the business of representation; verisimilitude had become a cheap technology. But Turner was wrong—the photograph didn’t kill art, it just forced painters to seek out new cultural markets. Instead of aiming for realism, they began experimenting with abstraction, focusing less on the depiction of objective reality and more on its subjective qualities. The camera opened up space for Cezanne.

Or consider basketball, a game that has been transformed by the “innovation” of the 3-point shot. Although it might seem obvious that three-pointers would increase the value of guards—they’re the ones most likely to take the shot—Gannaway et al. showed that the players who have gained the most value in the NBA labor market are tall centers who play close to the basket.

What explains this counterintuitive result? Defensive strategy. When players move out to contest three-pointers, they leave more space for the interior game. Furthermore, the long ball can be taught, as evidenced by the NBA’s steadily rising three-point field goal percentage. (In 1983, teams made 23.8 percent of their three-pointers; in the 2017-2018 season, they made 36.2 percent.) What can’t be taught is height.

Or look at the effects of the great disruption of our time: computers. Last year, I wrote about the effects of digital technology on human capital. Interestingly, the widespread adoption of software seems to be increasing the value of social skills. At first glance, this makes little sense. Shouldn’t the computer age reward those minds best at computation? However, the researchers found that many cognitive skills are easily replaced by cheap machines. As a result, employers increasingly seek out humans who are adept at the very things software can’t do, such as manage other people and settle interpersonal issues.

We live in a time of relentless technological change. These case studies help explain why such change is so unsettling. Our inventions aren’t just altering the competitive landscape—they are doing so in completely unpredictable ways. Those older tennis players probably thought the oversize racket would help them compete with younger players, compensating for their slight decline in athleticism and speed. They were wrong.

And the cascade of unexpected consequences never stops; when it comes to the impact of technology, change is the only constant. The rise of abstract expressionism created a resurgent demand for realist portraiture; in the current NBA game, the most valuable players aren’t just big men—they’re big men who can also hit three pointers. (There’s a reason Boogie Cousins averaged more than six three-point shots per game last year.)

Tennis is no exception. For nearly twenty-five years, the percentage of matches involving older players remained below the levels of the wooden racket age; composites had turned the sport into a young person’s game. But then, starting around 2000, the share of matches involving players older than 30 began to steadily increase. By 2014, these veterans played in a higher percentage of matches than ever before.

What's more, these older players are dominating the sport. As I write this, the top ranked player is 31-year-old Rafael Nadal. He’s closely followed by 36-year old Roger Federer, the greatest player of all time and recent Australian Open champion.*

Both men use the latest composite rackets. Their shots are loaded with topspin.

Fillmore, Ian, and Jonathan D. Hall. "Technological Change and Obsolete Skills: Evidence from Men’s Professional Tennis." (2018).

*Serena Williams continues to dominate the women’s tour at the age of 36.