I Don’t See Any Evidence That We’ll Live Hundreds of Years
I’ve been told that I could live for hundreds if not thousands of years. That technology will stop and even reverse the progress of aging. And I’ve been told this by some pretty smart people, like famed inventor Ray Kurzweil and accomplished scientist Aubrey DeGray. There’s even an entire TED Theme called “Might You Live A Good Deal Longer?”. And I must say, I’m tempted to believe them. Technology has come a long way since I was born, and it looks like there are some amazing breakthroughs on the horizon.
But I feel like, if this is really true, we should see clear statistical evidence of it. Kurzweil’s predictions of the future center around technology progressing exponentially, which makes it possible to see these trends coming. And yet he produces no such graph in his TED Talk, just a table with four values. I also didn’t hear anything about it in school, the relevant Wikipedia articles make no conclusive claims, and I have yet to see a good argument float up on Reddit or Hacker News. So I decided to go take a look. In particular, I went looking at how the data used to calculate life expectancy has been changing over time to see where the trend is going. This underlying data are called “life tables”, which are just a big lists of your chances in a particular year of dying at a particular age. The US Government has been collecting these in usable form since 1933, and they make it publicly available through the National Center for Health Statistics. Researches who study this sort of thing have processed it for computer analysis, and I examined it in Stata.
I don’t see any evidence that we could live hundreds of years.
The simple explanation is that there are two competing forces: progress (technology, knowledge, etc.) and aging. In the next year, progress will decrease the chances of someone your age dying, and aging will increase it. To truly stop aging, these two forces must be equal. In other words, progress must decrease your mortality rate by an amount that exactly balances out aging, so that your chances of dying do not increase with age. To defeat aging, the force of progress must be greater, so that your chances of dying go down every year.
Unfortunately neither of these appear to be the case now or in the foreseeable future. Average progress across all ages is indeed exponential, and it has a growth rate of about 2%. This means that a year from now you will be about 2% less likely to die than someone who is a year older than you right now. Unfortunately the progress of aging is also exponential, and its growth rate is about 8%. This means that someone a year older than you is about 8% more likely to die than you are. So while progress is exponential, aging is as well, and it’s growth rate is significantly higher.
The reality is actually worse than this makes it sound, because while the average progress across all ages is 2%, these gains are not evenly distributed. Most of them go to people younger than yourself. For instance, progress for a child in its first year is about 5% per year, whereas progress for an elderly person in their 100th year is about 0.1% per year. This means that the life curve isn’t so much flattening out or even shifting out but rectangularizing. More and more of the population will live healthily to an old age, but they’re not going to start living hundreds of years. At least not in our lifetimes.
I’ll show some data to back up these claims below.
The Force of Progress
The good news is that the chance of someone your age dying is as low as it’s ever been, and it’s falling exponentially! A 60 year-old has less than half the chance of dying as they would have had 75 years ago, down from 2.3% to about 0.9%. Our biggest gains are actually for newborns, which have historically had very high mortality rates. Just a few hundred years ago a quarter of people buried their child in its first year! Your chances of burying your child in its first year are a tenth of what they were 75 years ago, down from just over 6% to about 0.6%.
To know where these curves will go in the future, we take a look at the rate of change in the past. To do this we calculate the percentage change between each year, averaged across all ages. While it does vary a bit over time, it’s actually remarkably stable, which means smooth exponential decay. Each year the average chance of dying across all ages is about 2% lower than it was the year before. Just as importantly, while mortality rates have fallen dramatically, the percentage rate at which they are falling hasn’t changed much in the last 75 years. If anything, we’re making less progress each year as time goes on.
While 2% per year might sound small, it’s not. A 2% decay per year leads a value to fall in half in about 34 years, and then to fall in half in the next 34 years after that, and so forth. But as I mentioned before this progress is not the same for all ages, with the chance of a 1-year-old dying falling in half roughly every 17 years, and the chance of a 70-year-old phone falling in half roughly every 53 years. Most of the gains we’ve made are in the first twenty years of life, with progress for older ages appearing to slow almost to a halt.
The Force of Aging
We’ve known for a long time that aging progresses exponentially. This was discovered by famed actuary Benjamin Gompertz in 1825. He claimed that your chance of dying doubles every 8 years. This implies an average rate of about 9% per year. This is very, very fast, with doubles every 9 years.
As Gompertz himself noted, this progression very accurately describes the mortality curve between the ages of about 30 and 80. The mortality rate actually falls every year for the first ten years as children escape from (or succumb to) the dangers of entering the world. The rate then spikes up through the teenage years before smoothing out. Late in life mortality slows its increase. The curve must inevitably be an S-curve instead of a true exponential because the mortality rate cannot increase above 100%. In fact, there is evidence to suggest that the mortality rate flattens out at very old ages somewhere between 40% and 50%. Still though, at these rates someone cannot live for every long.
No Evidence That We’ll Live Hundreds of Years
Putting it all together, I just don’t see any evidence here that we could live for hundreds of years. As I mentioned above, to truly stop aging the advance of progress must as quick or quicker than than that of aging. What we see is just the opposite – progress, while fantastic, advances significantly slower than aging. Furthermore, progress does not seem to be accelerating and on pace to overcome aging in the future. What we see is just the opposite – average advances have been slowing over time.
It does look like we will live longer than any of those who came before us, but it doesn’t look like we’ll live for hundreds of years.