This is a surfer’s dream: catching a great wave, far from the shore, and riding it for long beautiful moments as it stretches further and further gathering momentum until the very end, when it breaks right at the beach. This is how my generation, born in the 1970s (when the Beach Boys released their iconic Surf’s Up album ), should feel, as we are riding on a “global demographic wave” which keeps extending further and further.
From a demographic standpoint, this generation is different from the previous one in two fundamental ways: it is both less “fertile” and more “durable.” We all live longer than our parents – dramatically so in emerging economies – and smaller families are becoming the norm. This is also why we will soon need to say “good bye” to the “population pyramid ,” one of the key defining concepts for any high-school or university student of our time. The next generation of students will learn instead about the “population barrel.” Already today, the pyramid is gone. The distribution of world population has the shape of a bell (see Figure 1).
This may seem counterintuitive. Given that population growth is at near record levels, with world population adding another “net” 80 million each year why is the pyramid is not expanding further? As this blog  pointed out four years ago, today’s rapid population growth is driven by longevity, and no longer by high fertility: there are more and more adults in the world. This is why we can experience both declining fertility and rapid population growth at the same time.
By 2050, there will be an additional 2.2 billion people in the world, bringing the total to approximately 9.5 billion (or about 30 percent more than we are today). Roughly speaking, Africa and Asia will each grow by a billion, while the rest of world will add some 200 million. Collectively we will be significantly older too.
To get at the bottom of this phenomenon we project the breakdown of these additional 2.2 billion by age group, both in absolute terms and compared to their current size. Here are the results (see also Figure 2):
- Children and teenagers (0-19 years) will remain the largest group but only grow modestly from 2.5 billion to 2.7 billion (an increase of 8 percent);
- Young adults and parents (20-39 years) will only see modest changes (the biggest shifts in this group already happened over the last 30 years) growing from 2.2 to 2.6 billion (a 14 percent increase);
- The "new middle aged" (40-59 years) will experience major growth. Rising from 1.7 billion today to 2.2 billion in 2050, this group will add more than half a billion people (plus 38 percent);
- The grandparents (60-79 years) will gain the most and more than double in size from 760 million to 1.6 billion (a 100 percent increase);
- The new “oldies” (80+) are also expected to rise sharply but from a very low base. From 120 million today, they should add another 380 million by 2050 (plus 211%).
The bulk of future population growth – more than 1.4 billion – will happen in the middle of the distribution. Those born in my generation and the ones right after will be between 40 and 79 years by 2050: they will fill up the top half of the barrel. And if they stay healthy  enough, they will then join a small but rapidly growing group of octogenarians still listening to the Beach Boys and, why not, surfing their retirement away!