Our fact challenged Treasurer, Joe Hockey raised some eyebrows when he suggested that we need to reform Medicare because children born today might live to 150. He got some support from University of New South Wales faculty of medicine dean Peter Smith, who cited the increase in life expectancy over the last century, from 55/59 (for men and women respectively) in 1910 to 80/84 today.

There’s an apparent paradox here: If life expectancy is 80/84 years today, how can a newborn child expect to live 150 years. The answer is that “life expectancy” is nothing of the sort. It’s the average age at death if current age-specific mortality rates remain unchanged. On average, people born in 1910 actually lived well beyond their “life expectancy” because death rates fell through their lifetime. So, if medical progress continues, people born today may live, on average, well past 80/84.

But how much more? Unfortunately, on past indications, not much more. Most of the 20th century extension of life expectancy came from a reduction in death rates for the young. A 65-year old in 1910 could expect to live to 76/78 (since death rates don’t change much over a decade, that’s an actual expectation not just a statistical construct). Today, that’s increased to 84/87, from 11/13 years of extra life to 19/22. For Hockey to be right, over the next 100 years or so, the conditional expectancy has to rise five-fold, to 85 years. The basis for all this, it seems, is a 2011 press release of the kind we see every week or two announcing a breakthrough that might, perhaps, lead to a cure for this or that disease.

But even in the unlikely event that this extension of life occurs, what possible relevance could it have to the amount we should pay for medical care today? Even under current rules (which would certainly change with extended life expectancy) Hockey’s hypothetical Methuselah wouldn’t be eligible for the age pension until 2085 and (given the anti-aging breakthrough he hypothesises) wouldn’t seriously burden the health care system until well into the 22nd century. Coming from a government that dismisses concerns about climate change as a problem for the indefinite future, this solicitude for Treasurers yet unborn seems misplaced.

Update Via Twitter, I discover that the source of Hockey’s claim is someone called Aubry de Grey, who is obviously in the tradition of wealthy British eccentrics, with his own foundation, journal and so on; a much more appealing instance of this kind of thing than Lord Monckton, but still not to be taken seriously.

Further update Defending Hockey’s silliness, Mark Kenny makes the point that what Hockey actually said (restating de Grey) was that it is “remarkable that somewhere in the world today, it is highly probable, a child has been born who will live to be 150”. This shift from mean to maximum helps the demographic plausibility of Hockey’s case, but only marginally (we still need an advance of nearly 30 years on 122, the longest lifespan ever recorded), but it makes the argument even weaker. Suppose that some child in, say, China is going to live to 150. What possible impact can that have on our health system. More generally, what can it matter to the budget if a handful of people live very long lives. It’s the average (measured by numbers like life expectancy at 65) that matters. As an indication of the minuscule scale of the fiscal problem posed by those with very long lives, there are currently only about 4250 Australians aged over 100, amounting to about 0.02 per cent of our population.

Yet further update It’s worth pointing out that, with pension age eligibility rising from 65/60 when the age pension was introduced around 1910 to 70/70 by 2035, men will have lost half of the extra retirement years gained from higher life expectancy and women the whole gain. The big problem we face is underemployment of prime-age workers, not the fact that we aren’t dying early enough.