Unfortunately, the same is not true of human processes, since, unlike trees, we (well, some few of us) control the supporting environment. Sometimes, in some places, the environment is conducive to growth in some aspect of human-kind. Generally, this is due to a self-administered advantage. The banksters, for example, made their $$$ by bending/changing/ignoring the rules of play. They won, and when they were caught cheating, pretty much got away with the filthy lucre. Nice work if you can get it.
Much the same transference of thought goes on in the field of demographics, most often by those who know little about the subject. Josh Barro recently flapped his gums on the subject. Being coy, he framed his analysis with "good news, bad news" meme. Using the title, "Your Kids Will Live Longer Than You Thought" doesn't help.
you need to look at cohort life expectancy, a statistic that adjusts for the fact that death rates tend to decline over time as health and safety improve.
As I noted at the beginning: people live longer today than they did in 1900 not because of some deus ex machina perpetual propulsion, but because some humans figured out how to staunch various methods of early death, notably infant mortality in the period from 1900 to 1960. It wasn't magic, or God, that led to the longer life expectancy at birth. If one goes, as I have urged many times before, and looks at the real data, one sees that life expectancy at age 65 (the metric that matters when discussing Social Security or retirement generally) has increased by a small fraction of at-birth. A really small fraction.
Medicine, these days, is largely concerned with adding a few weeks or months to the terminally ill geezers. Whether we should be wasting so much moolah on geezers is a valid question. The War on Cancer has gone about as well as the ones in the Middle East.
The Technical Panel on Assumptions and Methods established by the Social Security Advisory Board, an independent government agency that advises Social Security's trustees on matters including actuarial assumptions, says Social Security is systematically underestimating future declines in mortality rates, and therefore underestimating the likely life spans of young Americans.
This statement is the Tree Growth Proposal: there's been a continual, but with diminishing incremental effect, decline in early death up to now, so there has to be more decline in the future. We're not trees, and why we die early is mostly up to our behavior. Either we stop doing deadly things (smoking) or we find in medicine (surgeries, drugs, vaccines, etc.) specific therapies to slow or halt specific causes of early death. There is no deus ex machina.
Without specifics as to why, and where from, such future declines will increase I say, "horse shit". We know what causes most early death, and drugs and vaccines have eliminated most of them. Lung cancer has diminished as people are shamed into quitting and not starting. Smallpox is officially gone. Mostly, same for tuberculosis, flu, polio, and so on. The main cause of early death in the Rich West is too many calories, while in the Poor East it is too few.
In the long run, the Social Security Administration assumes the "mortality improvement rate" will be 0.71 percent -- that is, the odds of dying at a given age will fall, on average, that much each year.
Again, more horse shit, without specifics. We are not trees. We won't live longer if you just give us more water and more nitrogen. Gad.