One day in 1980, when I was 10, I sat in my great-grandmother’s living room and poured out questions about what life was like for her as a girl in Belarus. At 90, she was still sharp and could answer my questions. But she didn’t betray any of the emotion I hoped for. Born in 1890, in a tiny village powered by horses and the sun in a manner hardly changed from the time of ancient Rome, she grew up to witness the invention of the airplane and the adoption of electricity and the telephone. I wanted her to join me in marveling at this series of world-changing transformations, which I knew were beyond anything her girlhood self could have imagined. She just answered my questions calmly, politely. ‘‘No, I don’t remember the first airplane I saw.’’ ‘‘No, I don’t remember the first person I called on a telephone.’’  A key question in economics today is: Does technological advancement, and the improvement in average people’s material conditions that it creates, continue upward at a steady rate? Or has it already peaked? It’s no small question. If we have learned anything, it is that peace, democratic values and even self-reported happiness are closely connected with economic growth. Economies that are stagnant lead to conflict; if the pie isn’t getting bigger, after all, the only way to improve your lot is to grab someone else’s slice. It’s telling to look at the current presidential campaign through this lens. Bernie Sanders is arguing that this stagnant-pie-stealing has been going on for some time, while Donald Trump says that he can keep outsiders away from our desserts altogether. In a nation whose politics have long been characterized by indefatigable optimism — in rhetoric if not in reality — it’s striking that no presidential candidate in 2016 is offering an expansive, optimistic vision of the future.  In articulating such a vision, the candidates will find little help in Robert Gordon’s ‘‘The Rise and Fall of American Growth.’’ Published by Princeton University Press last month, the book is this year’s equivalent to Thomas Piketty’s ‘‘Capital in the 21st Century’’: an essential read for all economists, who are unanimously floored by its boldness and scope even if they don’t agree with its conclusions. Through a careful study of the entire history of American technological advancement, Gordon concludes that despite all the upheaval of the past 200 years, there have really been only a handful of fundamental steps forward: electricity, the telephone, the combustion engine, mass production, indoor plumbing, the conquest of infectious diseases and the computer. He argues that everything else, including the Internet and the smartphone, is simply a variation on these themes — and that for all our 21st-century talk of ‘‘innovation,’’ the pace of real transformative innovation has radically slowed during the past half-century.  We can see this, he argues, in the diminishing impact on productivity in the American work force. Productivity growth, at its simplest, means that people can achieve more in a given amount of time than they used to be able to. It’s the only way that human beings, as a group, can become better off. There was an enormous upward shift in productivity between 1920 and 1970, a rate of growth unseen at any other time in human history. But after 1970, that growth slowed. Then there was another, lesser blip upward during the years surrounding 2000, as computers went mainstream and became married to communication, in the form of the Internet. If we exclude that blip, though, the past 50 years have seen roughly half the rate of productivity growth as the 50 that preceded them. Gordon argues that this relatively slow growth in productivity, together with rising inequality, helps explain not just the stagnation in American wages but the general feeling of anger and despair. Worse, he argues that this post-1970 sluggishness is with us to stay, because the remarkable series of inventions of the previous 100 years is unlikely to be repeated.  The strongest backlash against Gordon has come from techno-optimists in Silicon Valley, who assure us that more wonders are coming soon. They point out that even the things we already know about — robots, drones, artificial intelligence, smart devices — will be sufficient to significantly improve productivity once they have been fully unleashed. Better still, they argue, there will also be new, radical inventions that we can’t even predict yet.  I, too, am more optimistic than Gordon, but for reasons that have little to do with future technological advances. As Gordon acknowledges, there is generally a long gap between a new technology’s invention and its wide impact on productivity. Primitive steam engines began appearing in the 17th century, and the telephone was patented in 1876. Yet we didn’t see that huge spike in productivity until 1920.  That’s because productivity, and our lives in general, improve not at the moment of invention but when society creates the conditions to allow new ideas to become integrated into our daily lives. The basic technological conditions for the expansive productivity growth of the 1950s and 1960s existed in 1900 and, arguably, long before that. But society had to do a lot of work first. There had to be new schools (only about 10 percent of Americans attended high school in 1900, and far fewer went to college) so that people had the education to use the new inventions. Unions and the modern corporation matured to help allocate labor. A new political system evolved to fit an economy that operated nationally, not just as far as a mule could walk.  It was, of course, a messy, often ugly, nonlinear process. The single hardest task was internal: Americans had to change how they thought about themselves. Not only did some of the iconic jobs of the 20th century not exist in the 19th century; they weren’t conceivable. There weren’t many large corporations, so there was less of a tradition of specialized jobs with narrow tasks. People had to learn to think of national markets, huge firms, accredited professions, new forms of urban identity. While writing this column, I was emailing with a friend, a woman who does brand marketing for a credit-card company. It occurred to me that literally every noun in her job title would have made no sense to her great-grandmother, or to mine.  The very evidence Gordon cites for pessimism — persistent inequality, low productivity growth, lack of major innovations — can also be read as signs of opportunity. In the last century, the main way a person’s productivity rose was by going to work at a large company and doing what the boss said. Today, lots of people are finding ways to improve their own lot — and overall productivity — on their own. They sell crafts on Etsy, get funding on Kickstarter, build toys with 3-D printers. They learn through online classes and prove their skills on sites like Topcoder.  Right now, the benefits of this digital, shared, distributed economy are accruing only to a tiny group of people and, even more, to the companies that serve them. But it’s at least conceivable that digital technology could help build new models of education, new ways for workers to collectively bargain, new tools to allow more people to identify and sell their skills and ideas to those who want them. There could be financial products that make it easier to withstand increasing volatility and insecurity. There could be an easier path to entrepreneurship, so more people with good ideas could present them to the market.  I called Gordon and described this vision to him. He replied, with a kind chuckle: ‘‘You are in a dream world. Your list of needed improvements in institutions and society are a wish list that isn’t happening now and is very unlikely to happen in the future.’’ And maybe he’s right. The language of the current presidential campaign — when it’s coherent at all — is of taxes and regulation, immigration and carpet-bombing. It is the language of zero-sum stagnancy, not expansive, shared growth. But it’s worth being clear: If we are indeed doomed to a generation of slow growth, it’s a lapse in our collective imagination, not in technological innovation, that is holding us back.  Adam Davidson is a founder of NPR’s ‘‘Planet Money’’ and a contributing writer for the magazine.  Sign up for our newsletter to get the best of The New York Times Magazine delivered to your inbox every week.  A version of this article appears in print on February 21, 2016, on page MM16 of the Sunday Magazine with the headline: The Imagination Gap. Today's Paper|Subscribe
The pace of technological innovation may well determine the health of the American economy over time. But what matters most is how it changes us.