On such a full sea we are now afloat.

—WILLIAM SHAKESPEARE

When I moved from investment banking to equity research in 1997, the first stock I covered was a company called CIE (pronounced SEE-a), a concert promoter and venue operator in Latin America. My job was to build a financial model, evaluate the management team, and look for possible catalysts that would drive the stock up or down. All this would lead to an investment recommendation: buy, hold, or sell.

After months of due diligence, it was time to go public with my recommendation for CIE. The valuation looked reasonable, but the stock was up considerably. What if I rated CIE a “buy” and the price immediately dropped? There wasn’t any obvious reason that it would go down, but afraid of looking foolish, I wanted to rate CIE “neutral”: if you don’t own, don’t buy; if you do, don’t sell. One colleague called me a shrinking violet. I own that. But then my boss, Jim Barrineau, prodded me, “Why wouldn’t it keep going up?” CIE was beating its numbers and seemed to have momentum. Stocks go up based on what you expect (future), not on what they were (past). If you expect the numbers to be good, that’s a growth stock. Barrineau asked why CIE wasn’t a buy.

I stopped shrinking and started stretching. I put a buy on the stock. This experience was formative in my career. It taught me how to pick a stock, but it also led me to a far more personal question. Asking myself, “Why couldn’t CIE keep going up?” eventually led to, “Do I believe I can keep growing?” This may seem like a nonintuitive leap, but that’s what I do: I look for how ideas apply to me, and to you.

With Clayton Christensen’s theory of disruptive innovation, I wondered how it might apply to people, which led to the framework of Personal Disruption. Studying E. M. Rogers’s Diffusion of Innovations and his S Curve paradigm gradually brought me to the S Curve of Learning.

But before I worked with Christensen and before I knew about Rogers, my work on CIE led me to wonder why people can’t be similar to a growth stock. As I grappled with a stock call that had the potential to put a sell on my career if I got it wrong, I asked myself the bigger question—Can humans keep growing?

It’s been two decades since I put a buy on CIE, and my answer is that our human capacity for growth is unbounded.

Stocks often do keep going up, and we can continue to grow.

Some things grow without help or intervention. Some unwittingly choose not to grow. We become a worn-out water lily in an overgrown pond like our Dear Abby friend Mr. Blah, who we met in the introduction. But through the ebb and flow of life, growth remains the default setting for human beings.

Growth is not inscrutable. The process through which humans change and ultimately chart their own destiny can be analyzed and replicated.

The S Curve of Learning is the model.

The first time I read Rogers’s Diffusion of Innovations, I encountered this quote from French sociologist Gabriel Tarde, written more than a hundred years ago: “A slow advance in the beginning, followed by rapid and uniformly accelerated progress, followed again by progress that continues to slacken until it finally stops: these are the three ages of invention.… If taken as a guide by the statistician and then by the sociologists, they would save many illusions.”¹

Applying Tarde’s wisdom to smart growth, we recognize the three stages of the S Curve of Learning: the slow advance of the launch point, the rapid, accelerating progress of the sweet spot, the waning progress in mastery.

On virtually any learning curve, the finite resources for growth will eventually be used up, the limits of carrying capacity will be reached and exceeded. Potential for growth in that specific situation will be exhausted.

But for human beings, growth need not stop. Our growth can be exponential; the more we grow, the more we can grow. There is never really a conclusion; there are only new beginnings.

In my early school years, I learned that the earth has five oceans. I was growing up near the largest of these, the Pacific, which covers more than 30 percent of the planet, an area greater than the landmass of all the continents combined. The Atlantic is next in size, then the Indian, Southern (Antarctic), and Arctic oceans.

Later, I learned that oceans and seas aren’t really the same thing; each ocean encompasses numerous seas—and straits and gulfs and bays. And later, still, I became aware that all this water can’t really be demarcated in this way; the five oceans are really one great ocean of innumerable waves rolling continuously over almost three-quarters of the earth’s surface, one into the next and then the next.

Every S Curve of Learning is a wave. Where there’s one wave, there are many thousands, infinite in variety. We can only ride a fraction of them in this lifetime. We want to be smart, pick our waves—direct our own growth—then use our ever-expanding capacity to help others do the same.

As with our planet’s single great ocean, there is one encompassing S Curve of Learning that is life, made up of contributing waves—a model for the human lifespan. At the launch point, we are infants, children, and adolescents. There is an enormous amount of learning to do, many mini-S Curve waves to master. By early adulthood, we have hopefully achieved a sufficient level of understanding and competence that we reach the tipping point of the life curve. Many years of productive work and valuable contributions follow—ideally, a lengthy prime of life spent scaling the exhilarating steep, sweet spot of our personal wave. Eventually, our progress slows as the wave of our life crests.

The S Curve of life, on inspection and introspection, is waves within waves within waves. Within the wave.