“An obvious explanation is that wealth buys health. And it seems plausible. Poorer people, at least in the United States, are less likely to have health insurance or access to medications.

But Dr. Fuchs says, then why don’t differences between rich and poor shrink in countries where everyone has health care?

“All you have to do is look at the experience of countries like England that have had health insurance for more than 40 years,” he says. “There is no diminution in the class differentials. It’s been the same in Sweden. It’s true everywhere.”

http://www.nytimes.com/2007/01/03/health/03aging.html

But more importantly, increased spending isn’t touching the astonishing rise in chronic illnesses from cancer through eczema (now more North Americans have this once rare autoimmune disorder than don’t. Of course, diabetes was once very rare, too, two hundred years ago.)

Many of these illnesses are tied to metabolic disorder, but it’s increasingly looking as though obesity and changes in appetite are a a downstream event in this disorder, not the cause. Successes in treatment are masking an outrageous growth in (chronic) disease, so concentrating on longevity is highly misleading. Spending isn’t touching this epidemic; I suspect because excess light exposure and consequent mitochondrial dysfunction isn’t getting much attention yet. (See photoperiodeffect.com) Until you know where to strike, having a fine hammer is of little use, and two hammers are no more use than one.

If he’s meeting you in a debate, and is an expert on the subject, it’s definitely a bad signal – if there was evidence, he should know it (though having evidence isn’t automatically a good signal, because of selection bias).

But in general, there are many reasons for people to adopt positions with indirect evidence – such as believing that the market price is the right one for a stock. Prediction markets are other indirect evidence, as are some “wisdom of crowds” situations and respecting certain experts.

Indirect evidence is sometimes in error, but it’s very hard to know when. It’s also not cumulative in the same way that direct evidence is. Two thousand successful experiments tell you more than one thousand experiments; finding a thousand more biologists who endorse evolution doesn’t tell you much more (which why indirect evidence isn’t generally allowed in those cases where a quasi-certainty is sought: science and courtrooms).

So if the person you’re talking to is rational, articulate and generally knowledgeable, but not an expert in the subject, the fact he can’t point to any direct evidence is “noise”. It dilutes the value of his position but does not contradict it. So it’s only a bad signal if the width of the noise is an issue – i.e. if you already nearly agree with him.

You seem rational, parsing and analysing David’s arguments, and pointing out where they come up short and where they didn’t. But there’s a problem with that:

These disagrement analysis are premised on the fact you can’t “agree to disagree“, so any disagrement must be irrational or dishonest. But that cuts both ways; if two honest and rational people always did agree simply by comparing their priors, then they would end up embracing a position without evidence to back it up. All they would be able to say is “someone I know, who is rational and honest, has priors in this direction”.

However, your comments “matter of judgment for him” and “his inability to point to any concrete supporting evidence” imply that you put great store by supporting evidence. Would you have thought his arguments stronger if he had simply said “I asked the opinion of someone knowledgeable and rational, and we agreed to agree, hence my position”?
David’s “judgement” may have been formed in just such conversations.

But there has not been anything else that I can think of that is as potent at reducing all-cause mortality.

In the same sense, the first drugs to treat a “type of condition” tend to be really important and later drugs add little extra benefit. Once you have one effective anti-inflammatory, the marginal benefit of the next one is much less (but you still pay the full development costs).

All that being said, even if I agree that the marginal benefit is small (and I need to think a lot more about this question), I think it is important to realize that we might get to a point on the cost-benefit curve where reduction of medical access could have rather surprisingly large adverse effects.

Why would you assume that?

I would assume that it is because smoking has declined, the air and water have been cleaned up to an almost unprecedented extent (could LA have less smog now than in pre-industrial times?!?), people are heavier than in the past (overweight BMIs have the lowest death rates), the service economy is vastly safer and healthier than the industrial economy, etc.

There is no clinical value of looking at the changes in the mix of medicines on aggregate. You could look at the # of prescriptions varying over time, take effect sizes from randomized trials, and model changes in mortality