Americans who are still considering which presidential candidate to vote for in 2020 may benefit from a century’s worth of historical context, which explains both how we got here and how our choices this November will influence where we are headed.

In our new book, “The Upswing: How America Came Together a Century Ago and How We Can Do It Again,” Professor Robert D. Putnam and I examine scores of measures spanning the full 20th century in order to explore whether during that time America was getting more or less equal, more or less politically cooperative, more or less socially connected and more or less culturally communitarian. What we discovered was, in a word, breathtaking.

Each of the core phenomena we examined follows a similar pattern — upward toward more equality, comity, connection and cultural solidarity for roughly six decades, and then, in a remarkably coordinated reversal, downward toward less. A single inverted U-curve provides a scientifically validated summary of the past 125 years in America’s story: The “I-we-I” curve — a gradual climb into greater interdependence and cooperation, followed by a steep descent into greater independence and egoism. It has been reflected in our experience of equality, our expression of democracy, our stock of social capital, our cultural orientation and our shared understanding of what this nation is all about.

America today looks eerily similar to the 1890s Gilded Age, when the gap between rich and poor was as wide as it has ever been. But in the intervening century we climbed to previously unseen heights of equality that came not at the cost of economic growth, but right along with it. And then we abruptly changed course and plunged right back into a deep chasm of income and wealth disparities — a trend that today shows no signs of reversing.

Both a cause of and explanation for extreme income inequality at the turn of the 20th century was social Darwinism, a culture of self-centeredness and devil-may-care narcissism. But then, as the Gilded Age gave way to the Progressive Era, reformers brought about a widespread moral awakening that ushered in a six-decade climb toward ever-greater heights of altruism. A trend which, in the 1960s, flipped in reverse, culminating in an America today that rivals the self-absorption of the Gilded Age.

As the industrial revolution moved millions of Americans out of tight-knit villages and towns and into crowded but anonymous cities, our social fabric frayed. But then, dissociation gave way to association as Americans invented new and innovative ways of bringing people together, creating a vast store of social capital that compounded for over 60 years. Until, in a now-familiar pattern, social bonds and bridges began suddenly to decay. Today we find ourselves less and less connected and cohesive year upon year.

Right along with social cohesion, political comity was also extremely low in 1900, but steadily rose thereafter, only to turn the corner right along with all the other phenomena we have outlined. On scores of different makers of political polarization America has never been more gridlocked than we are now — with the exception of the Civil War.

The American story in the 20th century is one of a long upswing toward increasing solidarity, followed by a steep downturn into increasing atomization. From ‘I’ to ‘we,’ and back again to ‘I.’ But none of these trends is inevitable. There is no predetermined arc of history that we are riding. Whether we continue in our downward drift or reverse course through a process of mastery depends entirely upon our exercise of agency — as individuals and communities but, in the moment of this election especially, as the American “we.”

Donald Trump did not cause the deep inequality, cultural narcissism, social fragmentation and political polarization we see today. But he epitomizes them. Joe Biden cannot reverse these long-run trends. But he has pledged to repudiate them. Perhaps, then, how we vote in this election says less about our party, policy preferences or political ideology, and more about which direction we want the country to move in: further down an ever-darkening path, or flip-turned in the direction of another upswing? The choice is ours.

Shaylyn Romney Garrett is the coauthor with Robert D. Putnam of “The Upswing: How America Came Together a Century Ago and How We Can Do It Again” and “American Grace: How Religion Divides and Unites Us.” She is also a founding contributor to “Weave: The Social Fabric Project,” an Aspen Institute initiative. Garrett holds a degree in government from Harvard University and is a returned Peace Corps volunteer. She lives in Washington, Utah.